It's more an aircraft decision for me. I'd take an LH A350 PY flight over an AC PY flight because I find the food and service on LH to be marginally better than AC and the 350 is a great aircraft on par with the 787. Having said that, I really despise the LH B747 planes so if that's my option I look to take AC.

Honestly, PY is nothing spectacular on any airline I've flown. I agree with some of the sentiments in here that suggest that PY only feels like an enhanced experience for the first 90 minutes. One thing I wish was controlled better is lav access. I'm being disgustingly elitist/DYKWIA here but I tire of the long queue of Y pax in the PY "cabin".