I have tried both - Smoktek DC tank and Parkes Chibi for regular steel cartos and a Parkes Acorn for CE2s.
I have to say, I bought the Acorn simply because I have three dozen CE2s or various types that I need to use. However, the Acorn requires the CE2 to be cut down, and I have found this to be a bit of a PITA.
Personal preference is for the carto tank - simply because there are many more resistance options available for cartos but, as always, YMMV.