The Q3+ was the best combination of tires I ran on my 919. The combination was very predictable and confidence inspiring. The tire wear was actually alright. Depends on how you ride but it gets pretty decent miles on the center, but if you do a lot on the sides, they'll wear out first. I ran I think 5 sets of Q3+ on my 919. Mileage ranged from 9500 on the rear to 5000, til the first cord showed, mind you. Trackdays and commuting, it was great.
I tried Rosso III next and it changed directions much more quickly but definitely was a step down on traction. Front tire felt vague and it wasn't a predictable turn in, felt a little too pointy of a tire for my liking.
Now I'm intentionally running a mismatched set of bridgestons, S22 rear tire and RS10 front. The front tire has exactly the same outer diameter and profile, only the compound and tread pattern is different. I don't hard ride in the rain so who cares. I wanted a sticky front and a longer lasting rear. The RS10 has roughly the grip of a q3+ but doesn't seem to warm up as quick, and it's not as firm. Still gives much better feedback than the rosso III ever did. S22 rear tire feels predictable. I've only done 200 miles on them so far, but I trust them to drag the peg on the ground and then some.
Q3+ is still my favorite set. I would try those first. I got the bridgestones for 180 bucks combined after the rebate though, so it's hard to beat the price.
I always change both tires as a set. If I am going to drastically change the way my bike handles, I'd like for it to be the way it was intended to handle. Although, the rosso iii rear with the Q3 front tire felt great. Putting a new rosso III on the front made the handling worse.