Surface RT or Surface Pro?
They still make the RT? Everything I read about it made it sound kind of pointless. The Pro is great for Office, but out of his price range. I sold my Pro because despite really liking it, it was more of a laptop and slightly awkward to use because of it.
I am not a 365 subscriber, but have read the reviews of the Office for iPad and people seem to be very impressed with it. If you don't become a subscriber you only read your docs. You can edit Word files in Pages though, which is free on iPad.