I'm pretty new to the pump part of paintballing, but i have used pump cockers before, but didnt like the idea of using a hopper so i went with a Phantom. The grip frame comes down to personal preference, i liked the 45 partially because i can get a set of grips for it. I took out my phantom for the first time yesterday and was quite surprised by its performance. I was told the Co2 wasnt going to be as efficient as it would be in a couple of months, but i was averaging 35 shots off a 12 gram, velocity was generally +/- 10 (it was 55-60 degrees out). Accuracy is easily the best point on this marker, i liked my autococker for its accuracy but this was landing shot on top of shot. It does take a bit getting used to the idea of 10/15 shots if your used to playing with a big setup, but you quickly adjust. Also theres no need to worry about batteries which makes this all that much better. It's a cheap alternative for playing, that also improves your skill while keeping paint within an affordable budget.
I'd reccomend it to people who are interested in pump play, its not too expensive, and theres not really any reliability issues.