if you want a top-shooting gun on the cheap look at
http://www.airsoftgi.com/product_inf...ducts_id=10847
internals of the higher end guns but nice light plastic externals, kids can carry them all day and they are 100x more fun and effective than the spring guns you's talking about.
there's a Walther P99 gas pistol that's in the $40 range that'll be more fun and closer in price to the spring guns
use the 20 or 25 bbs with these, stay away from the 12's
if you're dead set on a spring gun they're all about the same, just get the coolest looking one and have fun