Cargo hull + 2x impulse drive + survey module = 200BC, 6 speed in TA, 7 thanks to Impulse's speed boost.
Small hull + impulse drive + survey module = 135BC, 4 speed in TA, 5 thanks to Impulse's speed boost.
Tiny hull (!) + ion drive + survey module = 90BC, 3 speed in TA, 4 thanks to Impulse's speed boost.
None have range, but as a survey ship is about the only instance where it actually proves necessary, you might want to factor that in as well.
Drop cost by 20 on cargo to take up more space by using ions instead if miniaturization is sufficient (basic will do, but no range components will fit then). Drop cost by 10 on small to replace impulse drive with two ions, if miniaturization allows (basic leaves you room for range components, otherwise you're one short).
As Jonnan says, you can make an argument either way. Personally, I'd rather have 3 small survey ships than 2 cargo survey ships. Net speed is almost the same, with more of an edge going to small as more speed bonuses are stacked on. But the three smalls can go in three different directions-eventually one of the cargos will have to double back to pick up an anomaly my smalls have already gotten.
Don't forget build time, either-as I certainly hope you're not rush buying them. My first (additional) survey ship is out in 2/3 the time of yours, which is a marginal headstart even assuming equal industry output.
Tiny actually has both of them beat if you run it by the numbers, but they have too little space and hp to begin with to be worthwhile for a later upgrade.
TA does change things somewhat with its hp modules and the capability to add them to cargo hulls in particular, but I personally haven't found them overly worthwhile.