Rockets do more damage. Rockets have more splash. Rockets aren't weak as piss against ALL vehicles. Rockets will do better against people even if you don't hit directly.
Railgun has close to no splash. Splash damage from the Railgun does almost nothing. Railgun is weak as piss against every vehicle. If the Railgun misses, then it's completely wasted. --- Warhammer 40,000: Space Marine is god tier. There, I said it. http://goo.gl/6MEyA ~ Please click!
http://web.mit.edu/mouser/www/railgun/halluc/pictures/rg3.jpg --- "Sir, I don't think I'd care to look at a nun's legs. It'd be very impolite." "You'll just have to force yourself Godfrey. This is war!"