Disclaimer: I'm a noob here, but here's my 2c -
The best thing you can do is watch a thousand review vids over and over again (actually - not a thousand, just enough to get a feel for who knows what they're talking about and who doesn't). Decide what features are most important to you. Take the info with a tiny grain of salt since most are given the devices for review purposes.
But, if you watch enough of them, you do get to get a sense of what information is useful for you. You will probably make mistakes. You'll make purchases you will regret. You will also make purchases you love. You will
not only own one mod (you didn't think you would, did you?? lol). You will end up liking different devices for different reasons - portability, reliability, look and feel, various capability of the board(s)... At the end of the day, you have to just pick something that generally has good feedback and not a lot of negative feedback (read the comments) and just roll with it and see how it works for you.
FWIW - I'm a relative noob with regards to mods (coming from previous pen/stick style eGo devices I grew to despise) and I have an eLeaf Pico 75W, Vaporesso Nebula, and the Swag. I like them all for different reasons. Actually, I love them, but they aren't without their little quirks. The Swag is super portable - but I wish it were all metal, like the Pico. But the Pico is weird with how you turn it on & off and has no customizable curves (not that I'm using that right now). LOVE my Nebula, but it's bigger and I have yet to take it out of the house. I don't buy the kits - generally like to buy my attys separately. The Swag is limited to 22mm attys, so that's something to consider. Sometime you want something to take with you, other times you want something you'll keep at your desk or whatever that just feels more solid. And, I did consider the al85, but decided against it - don't remember why. I think Smok's attys are good, but I got a cheapo Smok Priv One before I got all this stuff, thinking it would be cool as a little pocket device - it's not. I
hate it. So, not sure I'd buy one of their mods again, but I'm looking forward to trying the atty.
Honestly, if you're down to choose between Smok and Vaporesso mods, I'd personally pick one of the Vaporessos. The Omni board is pretty cool. I'm liking it. (Of course I'm partial to Vaporesso so.... )
(That was a rather long-winded way of saying - pick the Vaporesso - either one, LOL)