I've not tried the Nautilus, and I've heard about equal good and bad on them... but everyone says when they work, they have good flavor / vapor. But, I have friends with Nautilus tanks, and side-by-side, I produce just as much vapor (using 50/50 juice and an AeroTank) as they do. I'm not a cloud-chaser, so vapor production for me is all about flavor and nicotine delivery... which my AeroTanks and KPT2's do just fine for that.
Now, for me, I love my Kanger ProTank2's and AeroTanks! I use an Air Flow Control base on the KPT2's, which really helps to dial-in your draw. As for vapor... I get plenty vapor from the KPT2's single-coils, and a bit more from the dual-coils on the AeroTanks. Coils are cheap... I've bought some as low as $0.75 each (in bulk), up to $1.60 each for duals... but if you look hard you can pick up 50-count boxes for $36 (single-coils) and $42-45 for dual-coils... so they're both under a buck a coil, which is 1/3 the price of Aspire coils... which still makes the Kanger's a bargain, IMO, even if you have to replace coils twice as often over the Nautilus! Another factor is that I've averaged <$10 tank on my KPT2's, and $13.99 avg each for my AeroTanks... so I can buy two AeroTanks or three KPT2's for the price of ONE Nautilus, with change left-over!
For me to invest in a Nautilus, they'd have to come WAY down in price, coils would have to be a buck each, and they would probably have to wash my car on occasion, too