I forget what bike it was on, but the last time I swapped from a suntour gt to a campagnolo NR, the NR shifted a lot better than I remember. But Suntours wore out and a NR didn't wear out nearly as quickly, so maybe that is an unfair comparison.
When I went to 9 speed on that bike, I went to a modern rear derailleur. Until last summer, I was shifting 9 speed with friction bar end shifters, so I'm not afraid of that part. Although with a 9 speed chain, if it's not totally in gear it's a good idea to fix that fairly quickly.