Well the biggest one to note is the ally doesn’t have a properly working SD card slot/reader as far as I know. And the deck isnt able to play most games with anti cheat.

But aside from those I guess it comes down to whatever is user friendly IMO and personally the deck is just that.

Where as when I’ve used the ally I felt like I kept getting lost or having trouble navigating with menus.

So for me it’s steam deck that wins.