All mine are in KKs with the exception of arboreals.
I am a lazy T keeper, KKs are just easiest and cheapest option for me.
My only criteria is KKs must have a black snap-on slatted/vented tops -- I hate colourful lids that clash with my decor.
It depends on the species. I mostly keep OW obligate burrowers and glass easily becomes too heavy to deal with. I prefer KK-style enclosures for my "baboons" and GBB. For my Asians, my "Pampho" and other tropical species, I prefer plastic boxes that I can drill ventilation holes in myself. Sure they are not as clear as glass or acrylic enclosures, but it makes having the right humidity so much easier than a KK.
Talking about juvenile/adults, for arboreals nothing IMO beats the European (mostly made in Germany) glass enclosures: cheap (really cheap), taller, easy to use, always available etc and with the price of one 'fancy' Exo Terra you can buy even four of those.
For obligate burrowers XL and XXL KK are perfectly fine.
It's hard to pick a favorite, as I use most of the different types, It really depends on the T, I do like plastic tubs cause of how well they retain humidity, their cheap cost and convenience. I do still enjoy setting up a few fancy exo-Terra enclosures for my larger arboreals.
I also keep an eye out for any food containers that could be converted in to a nice enclosure, so basically I use everything. I'd say my least favorite are aquarium style enclosures, they aren't great, take a crap ton of sub to fill up and are just super heavy.
I use a mix of everything from glass Exo Terra enclosures (for my arboreals) and repurposed aquariums to Kritter Keepers and plastic tubs so it's hard to pick a favourite, I most enjoy setting up the arboreal Exo Terra enclosures though.