I have a cool fire and have beat the snot out of it and I think it is one of the most comfortable mods made. Sorry for the people who have had a problem with it but over all, most people have had great luck with the CFIV and looking at the innokin thread, almost every one has good luck with the coolfire and innokin in general as far as durability. I am sure there are lemmons in every product, particularly relatively low priced electronics. Innokin is good about standing behind their products if you do have a problem.
All that being said, if I could only have one I would choose the MVP due to longer battery life. I am a low wattage vaper so the extra Watage isn't a concern for me. But, since I have gotten my CFIV, the MVP's sit on the desk for all but my longest all day/night outings.
Tanks well, that's on you. So many options and it depends on how you vape and what you want out of your topper.