Jim, I would second @proavia’s opinion about using the same for existing and new popup heads/valves so that you can manage the parts more easily. I don’t have an opinion on which water valve is better as I only have experience with A&A.
However, I would urge you to consider NOT adding a second distribution valve if at all possible. It will reduce some of your zones’ pressures (possibly require a higher cleaning RPM), and it will increase your high RPM “cleaning time” to get the same sweep coverage of your pool floor. If your proposed 9-zone system is implemented incorrectly, as I have seen in some user systems, it can more than triple your cleaning time requirement for the same sweep coverage. If done correctly, it will require a maze of rework plumbing that I personally wouldn’t trust any contractor to do without closely monitoring. In any case, it still will not be as effective/efficient as the 6-zone system.
Consider implementing your Baja shelf with just a single popup zone, and then swapping it in to replace the spa ‘s zone (I am assuming you have one). I have always had a hard time understanding how valuable that spa popup zone really is with the return drain in the main pool. Hopefully your automation would still allow you to run in a “spillover mode” (pool drain suction, spa return) to replenish the chlorine…if not, that would present an obstacle to that suggestion.
Edit: When I first responded, I thought you were proposing an 8-zone system (6>8)…then I saw you wanted 9-zones (6>9) You must be adding a huge baha shelf for those 3 additional zones. My suggestion to try to do it with ONE additional zone is probably not likely, sorry.