Having put a lot of miles on dual sport bikes squirming around on dirt roads, tramlining on a grooved road has never been an issue for me. But, the Pirellis that came on my Interceptor never felt stable or confidence inspiring. I replaced them when back tire wore out at 7800 miles. (The front showed hardly any wear.)
The Bridgestones transformed the bike. The handling is sharp and the bike feels glued to the ground. If riding fast in the twisties is a priority, have them install a set BT46s at the first service.
In the same sizes, the Bridgestones are lower than the stock tires but put as much rubber on the ground in the corners. A 110/80 front, and a 140/70 rear will be about the same height as stock, but put more rubber down when leaned over.