I am inclined to believe that Alphabet has far more experience in both AI and programming than Tesla, and that a Tesla with Waymo FSD technology would be ideal. I don't see the companies combining into "Toogla." I see Waymo licensing its autonomous-car technology to car makers, and I would love to be able to buy a Tesla with Waymo's FSD tech.
There are other companies with the mature quality-control capability to build more reliable cars than Tesla. But at present I don't see any company other than Tesla with the commitment to build full-featured electric cars in quantities to meet the market, and I definitely want my car to be electric. A Honda or a Toyota with Waymo FSD tech would be more reliable, but would probably be gas powered. Nissan seems committed to building EVs, but only at the lower end of range and performance, and most of their cars are gas powered, so if they built a FSD car it would more likely be gas than electric. A GM FSD car would almost certainly be gas powered for the same reason.
For all its flaws and shortcomings, Tesla is the one company fully committed to electric, so it's the company I would most want to build my Waymo-equipped car.