There's nothing inherently different about the purple Modify pistons, they are just breaking in setups that don't have carefully adjusted AoE, have pre-engagement or are pushing far too high a rate of fire for a plastic piston. On a related note, you're very rarely going to have an issue with even a simple beige Chinese piston if you are only firing in semi at like 350fps. Reliability is proven at the extremes.
Hence, if you're interested in reliability, the
only data that should matter in your research should be coming from people who are testing pistons in setups >400fps >30rps, because people who aren't stressing pistons out significantly are going to have a wild variation of opinions on pistons apropos of nothing in particular, or country-of-origin affinity, hence all these recommendations for magic pistons from the island of Japan
No offense intended to the fine people here, but I assure you that if you put any of those TM, Prometheus and other Japanese pistons into my Diablo without adjusting for AoE or paying attention to any other factors, they should get shredded in seconds. It is all about accounting for those factors. There are very few magical pistons out there.
My personal favourite is also the SHS metal racks like some of the guys above, but the latest batches of these have been super problematic for me. Your mileage may vary since data from various people suggests that bad pistons can hide in otherwise good batches.
You asked about Lonex. I've got a couple Lonex reds in the shop waiting to be tested. I've seen a couple of shredded Lonex blues for example, both in cases where AoE was not correctly adjusted and the strong SHS gears just went right through them. This isn't Lonex's fault. The red "extreme toughness" Lonex pistons are made of some kind of glass-fiber-reinforced nylon. The material feels extremely different from everything else I've held, but I wouldn't expect this to excuse me from adjusting AoE -- not even metal racks do that.
As always, and especially if you're super interested in getting good at rock-solid high performance builds, I'm going to say that it's more important to ensure proper interaction between your sector gear and piston's pickup teeth than to drool over recommendations from us. Verify a mid-range Modify purple running in your system for 5000 rounds at 25rps, then confidently run something much fancier once you've figured out what makes that all tick. Hell, kill a whole bag of shitty anonymous pistons on your way there. You'll learn a ton! (I literally have a big bag of dead pistons if you ever wanna see it..)
TL;DR: You do not need to pay a fortune for good pistons that can handle tremendously stressful setups, and mid-range pistons can survive mid-range stress for long periods of time with some basic adjustments.