In my experience,the better big barrel bats are -10 and under(I see your son uses a -12).That B1 is allready a good bat.I've heard good things about the Combat B2 big barrel but have not seen it so I cannot comment on it's performance.I can say that the Demarinni Vexxum(-10,2 5/8") and the Worth Prodigy Lithium(-10,2 3/4") are both good big barrel bats.The Vexxum is very durable whereas the early model Prodigy were denting very easily.
The only advantage I see with a big barrel bat vs. a 2 1/4" bat is a little more barrel flex(trampoline effect).I do not think it makes hitting the ball any easier.If you don't square it up,it will still pop it up or drive it into the ground.It is still a round bat hitting a round ball.
My son hits BP with a wood bat as well.