The second problem with the Protanks is that they are fidgety. They require a ton of fiddling to get it right. They are either flooding or getting dry hits seemingly all the time. They are really picky about the consistency of your e-liquid and I just don't have time to mess with them anymore. Folks who are successful with them typically rebuild their own coils for them. I don't have time for that either.
The last problem is flavor. I did a side by side with my Protank 2 and an Aspire tank a couple weeks ago using the same liquid and I couldn't believe just how bad the flavor was on the Protank. It was extremely muted...and my immediate thought was that any liquid I put into it was wasting the price of the liquid.
The bad on them is that they notoriously leak liquid through the center pin in the bottom of them. So it's a royal pain to keep your battery connection all nice and clean. They also tend to get gurgly at times. I know lots of folks who swear by these tanks. And that's fine. I don't hate them. I just don't really like them either. I'm told that the new iClear 30s is a big improvement in design, but haven't tried one yet.
One of the things that I absolutely love about carto tanks is the "crackle" of them. No other tanks or atomizers on the market seem to crackle quite as loudly as a good cartomizer. Coming from decades of smoking clove cigarettes, I'm pretty enamored with the crackle. Carto tanks are somewhat old technology, but they've come a long way. And I find myself more willing of late to venture into this old-school tech to give it another chance.
Of course the big downside to carto tanks is that you have to fill them very carefully or you'll make a gigantic mess. The engineering of them is downright stupid. It was a cobbled together solution to wrap a tank around a cartomizer. It worked, but it should have evolved WAY more than it has by now. And of course, any cartomizer has to be primed. It has to be soaked with liquid before you ever EVER fire it up. If you hit fire on a dry cartomizer, it's dead. Period. The end.
I can feed these a ton of power and they don't seem nearly as likely to burn as many other technologies. They produce large billowy clouds of vapor. And the flavor is excellent. In my opinion, it is just the tiniest bit muted from what I'm getting off the carto tank, but it is still at about 90% there. And unlike the carto tank, it's a piece of cake to pop a new head into the Aspire tank when it burns out. No e-liquid goes to waste in the process either. (In a cartomizer, any liquid soaked into the carto is thrown away with the carto when you replace it.)
I've started stocking up on replacement coils for my Aspire tanks since it seems that this is where I've landed as my go-to tank of choice every day. The coils aren't cheap. You can buy 5 of them for about $12. The good news is that for some of my e-liquids, I can use a coil for an entire month before needing to replace it. The bad news is that for my very favorite e-liquid, I have to replace the coil every 3-5 days. So your mileage may vary and whether it's worth it in the end is totally up to you. For the convenience and consistency, even if it's costing me $3-$6 a week in replacement coils, I'll pay it. My time is worth more than that. And if I'm putting a premium quality e-liquid into a tank, I want to be getting the very best performance I can.