ReBalls are awesome, chronoed around 250 ish they have a very simular trajectory and don't really hurt much different (unless you are twats and light each other up at close range)
Use reballs 10 times over and they have paid for themselves and then some. I'll be honest, not THAT feasable for individuals but perfect for indoor training. Pro team Joy Division can equate a great deal of their success to almost daily training indoors at their own ReBall facility at an almost non existant cost.
I recomend you pop to Fireball the paintball gym near Leeds that uses ReBalls. A flat fee of 20 quid (i think) and train and shoot as much as you want.