rowuk

"resistance" is a very controversial subject that has as much to do with your body use as with the hardware. Large and medium-large bores have no influence on the freeness of the blow. That is a myth that keeps coming back. The leadpipe, bell design, mouthpiece design all contribute to that which we call resistance - NOT THE BORE SIZE.
Generally, if you think that the high register is "stiffer" on your horn, YOU are not relaxed and hardware change will probably not really help. If you are relaxed upstairs, the horn is not that significant! The single biggest factor for "resistance" in the upper register is pressure on the upper lip not the wrong horn.
Instead of going on a hardware safari, you will gain more from a couple of yoga lessons or some professional embouchure tuning.
I know that this is not what many people want to hear. The magic of a new trumpet and the advertising promises are much often stronger then the urge to dissect ones own playing........................

__________________
Whenever I feel blue, I start breathing again.