Mainly those of durability. Also, I preferred the flavor the Aspire products produced. In my opinion (but one thing about flavor - it's VERY subjective), Aspire stuff gives WAY better flavor.
Listen, at first I thought that the Aerotank was all of it. I even learned all of the quirks...don't over tighten the wick, don't use too thick of a juice, push the fire button a little before I draw, let's rebuild a wick, take out the silica and use cotton....and a co-worker never fiddled with his stuff and it worked. That's how I found out about Aspire.
Also, the Aspire stuff is better built. For example, on the most basic of tanks, the Kanger chimneys tended to crack at the top, near the tip, allowing juice to run into the chimney.
The Kanger coils were hit and miss...both in resistance and in whether or not they would leak.
You should give the Aspire stuff a try - it's the same price, and you might like it better. I know that Kanger was the only reason that I ever considered stopping my vaping.
On the other hand, I should thank Kanger. Had I not had all of the problems, I wouldn't have tried RBA's.
Kanger is odd - many on ECF seem to like it, and then many are like me. Makes me wonder about suppliers.