I always wondered the same thing myself. I just sort of "kicked" a "habit" of running my zmax with a cirrus carto tank for about 2 months. I kept lookin at my reo sitting there and felt bad for it then had a realization. I threw a LR boge on my reo and no I haven't touched the zmax. I like that I can just fill the bottle instead of having to slide the tank and fill and blah blah. Plus when the carto on the tank goes bad there's always the hassle of having a new slotted ready to go. I get the same flavor just running the boge on the reo and its so simple. No fuss, lots of vapor and I just bring a spare battery or 2 on those days where im gone from the house for a long time. Bottom feeding is the way to go I will still say after a year of vaping.