I have some FermZillas and a Fermentasaurus, along with various Spike, Anvil, and SSBrewtech stainless conicals/buckets (only a couple of the Anvil buckets). I also have a ton of HDPE in Spiedel (awesome vessels if not super-heavy when full - I've always wanted on of their Eggs).
I do not use the plastic any longer, and haven't in over a decade. Not for beer at least. The conicals are so much easier to use, so much easier to clean, and so much easier to keep contaminate free from one batch to the next that plastic is more cumbersome, for me.
Though I do enjoy looking through the plastic and watching those bugs work. But the light also likes to look into it. So if you go that route, get jackets, or blankets, and don't forget to get a chiller that can go through the tiny opening so you can temp control it. Stainless conicals make that easier too. Though I do have some custom coils to fit in the opening of some esoteric fermenters, it is easier to buy off the shelf components that fit almost every single vessel out there.