In my 1500 point list, I field 2 units of 20. That way I still have a fair few to tarpit/contest objectives, but they're easier to move about. I can tell you from experience, moving 20 models about is bad enough, I don't want to try and work out CC attack range etc with 50 models.
That being said, I use mine as counter-assault, led by Jarran Kell. Kell charges in against a standard enemy trooper, and the conscripts swamp all the other enemies so they can't target Kell.
This way, Kell avoids being powerfisted, and usually only gets attacked by 1 guy a round, and he gets to kill a few baddies each turn with his PF. If the conscripts actually do anything, that's just bonus. 20 conscripts is good enough to swamp the enemy for the whole game, while still being able to maneouvre around the battlefield between units.
Same goes for any IC. And you all thought equipping an independant commissar with anything was a bad idea...