Maybe a little retro but you can't go wrong with a Russian 91%. A totally classic MTL RTA in my opinion and anyone who doesn't have one in their arsenal is missing out. The Russian 91% is the original clone and the only clone worth having!.
One drawback is that it's difficult to refill without flooding if the stainless steel tank is being employed simply because you cannot see when it's full until
juice starts leaking from everywhere, and i mean everywhere !!. Save yourself a massive headache and use the plastic tank instead.
Mistakes include trying to fill from the top. If the top is unscrewed it also unscews the chamber which in turn disturbs the wick in the wells and you'll find yourself not knowing why juice is pouring out from everywhere later on. Also the positive terminal including the insulator need to be kept in check. If the contact screw is adjusted the entire positive terminal block spins around. So the screw, positive block and the insulator all have to be aligned correctly and completely tightened up. Another mistake is trying to fill the tank to the very top. You'll find yourself wondering if it's ever going to fill and then eventually juice starts to pour out from everywhere.
I use my Russian on an IPV4 box mod with a sub ohm 0.83 coil made from 28g kanthal.
No other RTA or even any kind of tank has the reputation the Russian 91% has. It's in a class of it's own.