well, your asking these questions on a php board so opinions may be a little biased, but, php of course!
asp isn't half the language that php is. it has no mail / file upload / image manipulation capabilities (thats just for starters) and im afraid vbscript was never intended for the web.
.NET is another ball game, but from what ive seen its too bloated for the web.
and as for this...
Can MySQL handle shopping cart data well now? I know there was an issue about it for a while.
no idea what your talking about.