New laser tube for K40

[geartech]

First I've upgraded to the LO-X7,
Upgraded the opticswith new mirror stands and 25mm mirrors and a new cutter head with 25m mirror and 20mm focus lens
I'm loooking to replace the tube with something a little better, Cutting the case and putting the housing is not a problem
I can do all of that.

I'm just wondering if it's better to go with the 45w or 40w tube.
P/S will be upgraded as well in the future
Just trying to find out if there are any draw backs on the 45w vs the 40w tube in this setup?

Fred