I haven't tried the Pro Tank yet. Have one on the way from a trade. But I do not like the iClears at all. I have tried the 30, 30S, 16 and 16B. Do not like any of them. Of course I am an Aspire BDC fanboy since they just work for me. Love my MVP's. Just don't like the innokin line of clearos.
This just shows, that the "it depends" answer is probably the correct one. My experience with the Aspire heads, have not been good. Out of the 14 heads i originally purchased ( four that came with the devices and two additional 5 packs ), only four performed well. Thankfully i was able to rebuild them with 28g kanthal and cotton as a single coil, and the performance improved immeasurably,but because of the deterioration of the cotton fiber, it has a limited rebuild life. I have had a 100 % record with the iClear 30s coils however, and it produces more vapor. The flavor is a little muted, but the vapor is a lot warmer ( it's a top coil ), and that is what i like with my naturally extracted tobaccos.
There are many variables involved, and different devices suit different people, based on their vaping preferences ( draw style, power output etc...) and the juices they use, and whether they stick with stock coils or rebuild.
I haven't had any experience with the innokin bottom coils, but i have tried their top coils, and i like the iClear 16 and 30s, but not the 30 so much. For bottom coils, i prefer rebuilt kanger coils with an aerotank base. They are immeasurably better than the Aspire stock coils imo, but some may not be inclined to rebuild.
Btw, i just received my first Innokin IClear X.1, and it is taking a bath currently. It looks really nice, and i am hoping to be able to rebuild it ! I will post a thread on my impressions in a few hours after i have vaped on it for a while.