I've been using the D'addario 12s with a wound g on my HBii. But I'm tuning down to D standard. The 11s just made the piezo sound thin and flappy, like I was playing with a really thin pick no matter what.
I do have a set of flatwounds I'm going to put on next. Just chromes for now. Once I get the gauge right I'll but some spendy Euro strings.
I've got some flats on my DGT right now. I really dig the feel. And I don't find the change in tone to be anything I can't manage. My amps have tons of treble on tap... And I find that PRS guitars are generally bright to my ears. I run the tone at 5 as a rule... Whereas I run the tone at 8-10 on a gibby or strat.
I was a Slinky user for years, but found they were going dull on me recently. So I started back to D'addarios again.
Rotosounds were ok but felt a little weird. Dean Markleys die within 10 mins of contact with my skin. NYXLs aren't worth the cash for me. And cobalts are excellent exfoliators... But not super sounding for my purposes.
Before I started this reply I would have told you I don't play around with strings much.
I'm going to check out some of the other brands mentioned here... I've been seeking out different flats lately as I'm limited to chromes or TIs in Ottawa.