Great question to ask in a SCUBA forum so go ask this in a unbaised place not like this.
I do both and I have one question for you what kind of gun.
If it's an Angel buy the gun man you would be crazy not to,if it's a low to medium quality gun go scuba.Anything less than an Angel,bob's Long intimadator,Mini mag,Auto mag,Auto cocker, or bushmaster go scuba if it is one of those guns than make a choice and tell me b/c some of those guns are pushing it.
For the non paintballers here,here's a little perspective an Angel (which is a gun) costs about (this is for there best model)
$2900.00 that's right two thousand nine hundred dollars without tax.Paintball isn't some little kiddy game anymore.
So please only ppl who do both paintball and scuba reply to this post ok?