I've been using cartotanks almost exclusively for several months; been quite happy with their vapor and flavor production.
I decided to get a couple of AGA T2's to see what all the fuss was about. I'll say this up front. They have a much higher learning curve than cartotanks. They won't work right out of the box if you've never used one before. It may take a few re-builds of wick and coil before you get a superior vape from them. They can be frustrating and fussy (IMO).
Once you get them working perfectly, a cartotank is no match for them in vapor or flavor. However, in my particular case they have been inconsistant. I'm admittingly still a beginner and still learning. I've not had the time recently to devote to correcting the recent issues that I have had with mine. But I do have confidence that this can be a superior vape to a cartotank.
Regardless, you will need a good backup juice delivery device to use while you fiddle and experiment with an RBA. Whether that will be a cartomizer, clearomizer, a clearo tank or cartotank it doesn't matter, you need to always have a backup. Thank goodness my trusty cartotanks were there when my RBA's weren't performing up to par.