I think I have to revise my top 2. Xcloud lets you play games you don't own, but twice now playing destiny my controller lost connection to the character. Destiny 2 on Geforce now was superb, i find it even more responsive than the xcloud version. So from that both xcloud share position 1.
Update on my experiement: I've tried Prime OS on an old laptop but xcloud, geforce now would install but not load. Not sure if thats the old tech or the OS, thinking I may have to dual boot prime os on my main pc to rule that out....
Prime OS does allow you to play using the xcloud and Geforce app. First hurdle out the way, now the hardware....