Not quite sure what the difference between a rba and rta is?
As Doug says above.
With a tank you have factory coil heads and possibly an RBA head as well.
Usually... the RTA has no factory built heads, just a deck for your own builds.
They usually provide a larger area for builds and better flavor, as an RDA would.
But you must do the building.
As I said, if you accept, or prefer, to roll your own coils, adding RTAs to the search greatly expands your choices. Just food for thought (I love the things... and hate tiny, finicky RBA heads).