cocker vs. c-3

Those are entirely different guns for entirely different purposes.  It's like asking if you should get a motorcycle or a fishing rod.

Need more info.  What kind of player, what kind of game?  What are likes/dislikes?  Desires, wants?

Yeah, those are total opposite ends of the spectrum. We need more info on the type of player and games your friend plays.

I tried playing speedball with a C-3.  It didn't go so good.  Cockers are good for all-round use.

If they'll let you play - most stock-class rules prohibit constant air, and require rock 'n cock tube loaders.

But it would certainly be fine in any pump game, or any large-area woodsball game where there aren't many pitched battles.  Great for big (long) scenarios, since you never need to fill air.

Whats wrong with using a pump for speedball? I use my Phantom all the time
and its great for snap shooting. Of course, the C-3 still has a big, bulky
hopper on it, but it's quite simple to convert it semi-stockclass.