I'm inclined to agree with Simon on this one. If there is one thing I hate it's going through the motions on stage!!!! I think once you get to know each other's playing the rest falls into place so there's no need to thrash every note to death in rehearsal. We are incredibly lucky in a sense that we have a HUGE repertoire (takes away the boredom factor) which each of us have taken away and done our homework on, so this cuts our rehearsal time down quite drastically.
The 'Pictures' album you refer to was recorded in the early stages of my career in the group. At that point I didn't really think about any 'sound matching', though stylistically it had to be the same. If you're worried about trying to match up sounds it's probably a good idea to make sure your equipment is similar, i.e same mutes, blowers etc. Si and me play on Smith Watkins trumpets and I have to say that playing the same brand of instrument helps with intonation and other such things, though that wasn't the reason I changed from Yamaha.................. the Smith Watkins are just great blowers!
Good luck with it all, no doubt we'll be hearing more from you......