For me the Phiniacs are the most worry less carto tanks in my collection. Once it's set I don't have to worry about the caps coming off or the carto sliding out. But because they are so rock solid they are also a bit more of a chore to get set up with their mega tough o-ring seals. Lol
The Fluid Flask is super convenient but the carto can slip. I really wish it had a tighter o-ring on the bottom cap. The Kir Fanis just looks good on Provari. Functionally not a lot better than a simple Boge F16 tank, but it looks hot on the Provari and the fill port is nice.