I've visited Peru a good 15 plus times now and for the most part I book LAN. I find their service pretty much what I expect every time. I've found that Avianca starts making a lot of changes to flights and if you don't like it you're kinda screwed. I'm not too worried about the miles or the PQD (I don't do PQD anyway cause I'm not US Based)
I've taken other airlines and they're perfectly fine. I've taken a good 8 flights on Peruvian and they're pretty safe and have good flight availability.