Short version:
Paps X is 23mm, and I don't like it's airflow control. I wouldn't buy it over a normal Paps. And the Paps switch throw is too short for me...it almost feels like a touch sensor. It's phenomenal if you like that and a great mod. But, it's not for me.
The Poldiac switch is too complicated for its own good, and MMV wanted me to pay shipping both ways to replace a basically defective top cap. I would not do business with them again, but after I essentially re-tapped the 510 connection, it did work. It's a pain to clean and has more telescoping sections than a lot of mods, which means there's also more that you have to clean. I traded it for a Reo Grande and BF ERA, and I haven't missed it one little bit even though that atty sucks. I think I lost the ERA, so I essentially traded it for a readily-available $144 mod. I don't care.
The Nemesis....I can't find a flaw in mine except that the machining isn't quite as good as the Caravela and the engravings on the brass one are supposedly pretty shallow. I think It's gorgeous. It's button is the best solution for battery rattle in a no-spring mechanical. It'll take any normal battery configuration with or without a kick. There are a few different finishes to suit a lot of people's desires. The button throw is light, smooth, and relativley short while still actually moving. There are a lot of little bits & pieces to customize it if you want to. It looks great with my 2 favorite atties (fatty v2 and omega). It's probably about to become the 4th device ever that I've bought more than one of. The other 3 were
cigalikes (for battery life), ego Twists (for battery life), and Reos (because they're my desert island vape).
There are a lot of other options, though. Lots of people are obsessed with the Chi You. I definitely like my Turtle Ship. There's a veritable pile of Pionoy mods that work well. The atmizoo stuff is supposed to be awesome if you like side buttons. GGs still exist.
What are you looking for?