Latency-wise, I'm not sure how much better it currently *could* get. At least with xCloud, it seems you will have access to every game you already own, so you're not purchasing games all over again. That alone makes it much more appealing. Then add in game pass.
I may be wrong, but isn't one point of xCloud that if you own a Xbox One and/or PC, you can also download the games and play iflocally, the way PS Now also handles things? Which is a huge plus compared to what Google is offering, independent from having or not having to buy games.