I just followed the link that you posted and looked at the vivi. The cartos in my tank cost the same as those replaceable heads and seem like they are far less of a hassle. I'm not sure how those things work, but for the V4L tanks alls ya do is pull out the old cart and put the new one in. Filling it is super easy as all you do is pull the cart out a bit and just drip into the tank at a 45 degree angle and put a few drops in the filler of the carto then vape.
Replaceable heads are no hassle at all. You don't have to change them when you change a flavor. You don't need to reserve a carto for each flavor. You don't have to prime them. You don't have to worry about the holes being the right size for the juice you're using. There is no issue about vacuum forming and interfering with the juice feed. They last longer and taste cleaner.
You can re-coil Vivi heads for less than a nickel and in less time than it takes to dry burn them or clean them. You screw them in and leave them there until they get so gunked up you can't use them anymore. I usually go at least 2 weeks between re-coils and I've never had one burn out yet. I don't even bother cleaning them. When they get gunked up, I just put a new coil in the head. I have 12 heads that I got with 4 Vivi's and I'll probably never need to buy another head or carto again. Atomizer tanks, like the Vivi, also impart no extra polyester flavor to your juice like a filled carto.
I've used every type of carto out there. Tank or no tank, I'll never buy another carto or carto tank again. Since I can re-coil/re-wick a head in less than 5 minutes, I'll never buy another one of those again either. How economical can you get?
Oh, and you can carry them in your pocket without worrying about leaking. Don't try that with a DCT, or any other carto tank.