Barrel Length?

[Cossack]

I'm considering purchasing a T/C 50 cal. muzzleloader barrel for either the G2 Contender or Encore frames. The Encore barrel is approximately 2" longer and therefore heavier. The Contender barrel seems to handle better and would make the gun lighter overall. How will that 2" affect performance (velocity) if I opt for the shorter barrel?
Any other feedback from real shooters is appreciated: so far I only have salesmen opinions and none of them shoot either...
but claim that longer is the way to go.