The 2 are complimentary, not exclusive of each other.
The Domino is far superior as far as construction of face frames goes. The Zeta has the same restrictions as a biscuit joiner. The slots are just too wide for that. The Zeta shines as far as the connector application. The Tenso connectors are totally invisible and they will pull a joint together, which a Domino can't do. Dominos require an outside clamping force, and of course glue, which makes them irreversible. They are also great for edge-joining large panels, especially at an angle, where clamping is difficult/impossible.
I also like the Zeta Clamex more than the Domino connectors too. The access holes are far smaller (5mm vs 15mm) though they may not technically be as strong (as far as direct pull out force)
I don't recall ever using Zeta connectors alone? always with the alignment factor of at least a couple of Dominos, but I have used Dominos alone a lot of times. A clamping strategy and glue are required though.
Also, this is in a commercial cabinet shop situation, where the cost of both is not nearly as important would be to a hobby woodworker. Heck, a lot of people consider either to be too much.
If I had to choose? Domino, for sure, but I would feel the loss of the Zeta. (Likely because I have one though?, you don't miss what you never had)
Zeta alone? would be too lacking.....for me anyway. YMMV