Off.Playing with it on ruins the tech trees, ruins the point of individual races, and makes the game stupid easy.
Dunno, we all have our own definition of strictly relative consequences to a Tech-OFF gameplay.
Far from being easier, i find that it adds a pretty nifty strategic concern to "control" whatever pace at which the Universal knowledge gets;
a) Distributed between players - enemies or friendlies

Useful or wasted by the time anyone else reaches any point(s) in all trees (be it, different, common or exclusive)
c) to be the key factor in a faster Victory - or Defeat.
d) to the actual END of all things to know without lagging behind the LAST man standing.
e) to the optimal number of personally expended Beakers or equivalent resources in BCs spent and productivity focused on a bad ship design -- since, the weapons & defenses DO match up or not while into a synchro fashion provoqued by a smart(er-est) decision.
The particular issues of Tech-ON provides a much more exciting context to me and until, espionage gets enhanced i would need to wait to judge the irrelevancy of preciously kept unique techs as they may just be as essential to a race or even, to a team of INFLUENCERS! All differences being accounted for, the perception i have of opponents is still; If i lose (through any means, limited by optional OFFs & ONs) they win.
I've been a salesman in a home-renovation center in the past, so i might sound off-on a bit biased in how i perceive commercial gimmicks as opposed to conquest tricks (unique also if not shared, btw).