Just look at them and see what you like. Most of the high-end mods perform in the same ballpark. For the caravela-style ones, the big differences are in how they capture the battery and exactly what fiddling you have to do.
Some have "features" like airflow control (nemesis, chi you). But if you're using a Kayfun, that's irrelevant. Some can be turned into hybrid-like devices based on their thredding.
I think the right one to try first is the one that blows your hair back.
My personal favorite right now is the Nemesis. The battery adjustment is simple and straightforward. The lock ring is big and easy to use. I like the engravings. The fit & finish isn't perfect, but not much is (well...after you've held a Caravela). Anything resembling an issue I have with it is nit-picking. Unfortunatel, the secondary market for them is dead thanks to the

counterfeits. If you decide you want to sell or trade it, you'll have a hard time convincing all but the most gullible that it's real. I could see buying a second, but it'd be in an F5 war...I'd never buy one from an individual again without some way of being sure it's real.
If I don't buy another Nemesis, I'm seriously considering a Ba Gua as my next. I've never had a 14500 mod before, and I think it'd look really nice with a Penlope...or even just a rebuilt protank mini. Chances are, really, something will catch my eye and I'll figure out a way to buy it...like my Turtle Ship. It's a good mod...not as technically good as the Nemesis, but it's finishing feels excellent and it works great.