We hated...
* after lots of continuous shooting, the flash suddenly needed a very
long time to recover, and became very sluggish

Until you switch over to one of those flashes that doesn't use batteries,
this problem will continue to plague you. That isn't to say that other
cameras might not do "better" in this respect, but likely only because of
other trade-offs, like less powerful flash and use of higher ISO's, etc.
Remember that you said that you shot more images with this camera; are you
comparing apples to apples? Off camera flash or a grip that holds an extra
battery will help alleviate the problem.

Eric Miller
www.dyesscreek.com