Well they told you everything you need to know, but I am going to add to it... in the vaping world you have different delivery methods, you have clearomizers, cartos, a whole lot of options... that come premade, then when you get into rebuildables you have a few options too... you have your rebuildable tanks, and your rebuildable drippers, dripping is renowned as the purest of flavor, the best taste the best vapor... fresh juice on a coil... tanks are for convenience, so that you dont have to pull that tip, drip drip drip, vape... then repeat (you dont have to drip every hit, just saying) well Rob (the man who made the REO) loved dripping but hated the hassle... so he started making REOs, bottom fed devices, that you just screw on your atomizer, the way your talking RDA (rebuildable dripping atomizer) is going to be best for you, squonk (squeeze the bottle forcing juice up to the coil) and vape, and just repeat...
compared to the russian which you are going to have to worry about flooding, may get into genesis style atomizers, which you have to worry about wicking...
you are at a crossroads, one road is going to be fairly expensive and may inevitably lead you back here, the other will only be as expensive as you want it to be...
i have a REO grand, and a REO mini, and I want MORE MORE MORE MORE MORE!!!
its going to be kinda expensive for me, I want at least 3 grands and my 1 mini...
I wish you the best of luck with whatever you decide to do...