SW ships can just hyperspace in to close the range. The warp is too imprecise for maneuvers like that.
Okay, while I've been getting better about not derailing this thread, you've brought up a dead&done topic. And quite frankly, some of the sheer levels of stupid in your post are insulting. Like this comment.
1. Microjumping is a very difficult thing for SW ships. Yes, they can do it. No, it won't make a difference, as 40K ships tend to continue maneuvering in combat. And at much higher accelerative figures than Wars ships.
Further, getting up-close-and-personal with a 40K ship is a really bad idea. It's begging to get slagged.
2. You do realize that a talented Navigator could do such things? And that there are Inquisitorial vessels that are designed to come out of the Warp in planetary orbit, and unleash Exterminatus? You're severely underrating the Warp, and taking a position of "SW hyperdrives r awesum, all others looz", which is rather like the typical Trektard approach of <technobabble> beats whatever.
3. Keep in mind that 40K ships tend not to use EWAR all that much in a dedicated fashion. It does happen to a degree, mostly as a side-effect of void shields or the operating mechanism of holofields or shadowfields, but SW-style jammers will be lacking on 40K ships. So it's likely that neither side has a range advantage, per se.
Maybe, but if the Empire has an effect on the warp, they have far bigger problems.
And the Empire has shown no knowledge of or ability to manipulate the Warp. Your point is fallacious, to the point of stupidity. You're assuming the Empire can fiddle around with, to no detriment to themselves, a huge source of potential corruption and taint that they have not even discovered. The Force != the Warp.
Even if the Empire could have an effect on Warp-based technology, it would likely be of significant detriment to themselves as Chaos (an entirely Warp-based power) is basically the Dark Side turned up to 11,000,000. They've got no protection. No defense. The most likely occurence is a huge influx of servants to the Ruinous Powers.
"Colonies" in the Empire probably count for far more than a "colony" in the IoM. Most of the IoM navy is centuries old or more, while the Empire large portions of the Republic Navy in a few years. The IoM definitely has economic problems.
Once again, several fallacies.
1. Prove that a GE colony is larger/more capable than an IoM colony.
2. Prove the IoM has significant economic problems compared to the GE.
Further, the IoM navy is centuries old because the general consensus of the scientific body of the Imperium is that they've already discovered everything. Said institution (the Adeptus Mechanicus) may be lampooned as a bunch of religious nutjobs who have no grasp of actual science, but the conditions they work with (certain construction geometries can cause Warp possession of inanimate objects) really indicate that the AdMech are geniuses.
Also, IoM warships are centuries or millenia old because they are built to last. A GE star destroyer isn't built to last; it's designed to be refitted every decade or so, at a guess. An IoM warship will last, because it's unlikely it will be totally destroyed.
So the IoM have ships centuries old (which generally have superior construction and more reliable equipment, BTW. Dark Age relics FTW), but they need said ships.
Further, your point becomes nonsensical, as you say "the Empire large portions of the Republic Navy in a few years". I'm guessing what you meant to type was "the Empire replaced large portions of the Republic Navy in a few years", but consider the position of the GE versus that of the Republic; the Republic was trying to fend off a separatist power that had effectively become an external threat, whilst the Empire had to suppress internal rebellion and discontent.
Incidentally, said discontent is remarkably lacking in the IoM. Sure, the average citizen is a fairly downtrodden fellow, but he has no freaking clue just how bad it really is. And it is much, much better that way.
As an aside, it's likely that a IoM Sector Battlefleet (50-75 warships, patrols 200 light year cube of space (400,000 cubic lightyears)) is larger than a fleet dedicated to the control of a volume of territory of equivalent size.
Compared to years to months of the IoM.
You do realize, of course, that Warp travel is slow and unpredictable by virtue of the fact that it is populated by fucking demons?! Really now, I'm sure that SW ships will be able to manage there less-than-a-week trans-galactic travel times when there are a bunch of fucking demons trying to eat their souls while they fly through hyperspace /sarcasm.
In case you haven't noticed, 40K isn't a nice place. When using FTL carries a not-insignificant chance that you could be lost for centuries or even have your soul ripped out of your body, then ripped apart and/or devoured (or some combination thereof), then there's a pretty sensible chance that it's going to take some time.
The fact that hyperdrive is faster only confers a strategic advantage. It's a pretty significant advantage, yes. But not insurmountable. Neither side can intercept, or detect, the other until it's too late. There's also the slight issue that a warp-motor equipped vessel can simply sit in the Warp for as long as it pleases, then drop out and let the roaring of their guns be as the crying out of a billion voices (I've always wanted to use that line in some way/shape/form). By by star destroyer.....
It's slow as molasses anyway, so no harm done.
Refer to the above for refutation of the fact that hyperdrive confers such a huge advantage as to render Warp motors useless and irrelevant.
Also, it may be "slow as molasses", but it's also something the Empire cannot stop and cannot detect. There's a total surprise factor for each, but ironically there lies an advantage with the Imperium as they have an adversary with a superluminal drive system comparable to (actually superior if I'm honest) to the Empire. Which would be the Necrons.
But similarities end there so a comparison is an exercise in futility.
A world sized planet requires a world sized response. Which the Empire can provide, if we are going all-out.
1. First and foremost, depending on the era in question, the Empire might not actually have the Death Star. If this is the Imperial Remnant, then the best they get is maybe an Eclipse-class SSD or two. I'm not aware of if they acquired the Galaxy Gun, but it's hard to use a superweapon like that against a planet that can get up and leave.
As an aside, don't bother pulling Suncrusher wank out. We've no idea just how the Suncrusher's weapon works, or what effect it would have on a shielded target. There was also only one made that got blown up.
2. Aside from that, prove the Empire would immediately realize that the World Engine requires the attentions of the Death Star.
3. You discount the fact that Necrons have superior teleportation technology to the IoM, and actually 99% of 40K in general. And that a fucking flying Tomb World has probably got on the order of billions of fucking undead zombie robots that require anti-tank weapons to put down reliably. Simply put, DS1 or DS2 is fucked by the world engine. No teleportation defenses, no reason to expect any enemy would even try to board, let alone have the capability to do so.
On the ground, perhaps, but they are venerable in space.
Yes indeed, they are venerable in space. Or perhaps you meant "vulnerable", not "venerable"? In that case, I'm sorry to disappoint you, but Space Marine vessels tend to be of higher quality than comparable IoM Navy vessels. There's a difference of roles, but an Astartes Strike Cruiser, which is more heavily armed and armored, and is much faster in the Warp, than the Dauntless-class light cruiser (the closest IoM Navy vessel), is ironically of slightly lesser size and tonnage.
An Astartes fleet is smaller than that of the IoM by many orders of magnitude, but they're the best of the best. And that best of the best just happens to be better than what the Empire can provide.
That's why I said it would be interesting.
It really wouldn't. It'd be more of a one-sided harvest of the hated living, who revel in their despicable state of living-ness. Bunch of stupid meatbags /end grimdark humor.
In all likelyhood, it would be a one-sided slaughter. Necron warships, well, we actually have no idea just what the Necron military navy looks like. We know what their harvest ships look like, and that those can only be beaten by the IoM with 3-to-1 superiority of numbers or more, and considering IoM and GE have roughly equivalent firepower, the GE would be in a similar position.
It'd be easier on the GE, certainly, by virture of the fact that they have crazy-good mass production (though I'll note that a Lunar-class cruiser, standard warship of the IoM navy, could be built around on (above, actually) a world of savages in the course of eleven years). Also easier by virture of the GE having better (compared to the IoM) superluminal travel options, that almost rival the Necrons in capability.
If you want to respond to any of the above, USE THE PM FUNCTION.
TO THE OP:
I deeply apologize for this dreadfully long post. I've given the demand to respond via PM, so hopefully this won't clutter up the thread anymore.