There seems to be zero consensus on any of the replaceable coil systems. One could have to do with taste: I personally did not like the hotter taste of the top coils like the Vivi or Iclear 16.
If you check the reviews, PhilB loves the Aspire. Riptripper claims they have too many bad coils. Rebuilding a Kanger style is a snap; you can improve the flavor and throat hit dramatically by optimizing the wick/coil to your taste.
I agree with Riptripper on this one: 6 Aspire coils, only two worked for me, and I am not going to even attempt rebuilding them. I get a headache watching the rebuild of that double coil Aspire in that tiny space: no, no, a thousand times no!
Even with the stock coils, cloned or genuine, I never had an issue with leaking, and I have a whole bunch of different Kanger style tanks-some genuine, some clones (PT I&II, Mini, Evod and T3). There was the gurgle which was easy enough to control by topping off the tank before the level got too low. I only use them when I am out and about and cannot afford to have juice all over my clothes or leak in my kit. Gennies are a disaster if you lay them down. I am a consultant in my supposed retirement; stains on my white dress shirts and light colored suits are not good for the image.
Also, I have never had any vaporizer with a bottom air hole (lots of RBA's and RDA's don't have one), not leave some liquid in the base of the connector. Is it a leak, or is it a little bit of condensate or seepage? A little bit of wetness at the base is normal; if juice starts leaking out over your device, you have a leak.
I also got some of the Ismoka BC from Fasttech. They were dirt cheap. It has an air hole on the side rather than the bottom. It does not use the same coil replacements as the Kanger's. The first head was terrible; the second has worked fine.
So much of your experience will have to do with your PG/VG ratio, flavor type, vaping habits (long deep draw vs a puff) and device.
So, my only advice is: if it does not work for you, move on. Vaping has become so complicated with so many permutations, that one has to fiddle a lot to get there.
We can do so much with computer aided simulations to the point of testing aircraft, cars, buildings, bridges without even buying the first piece of metal, that one would think that an engineer could solve the problems of the vaporizers with ease.