I'm not a fan of the Surface Pro, I'm one of those 'it's not a good laptop, it's not a good tablet' people. HOWEVER, I'm glad it exists and sells well enough to sustain its existance as a full conventional PC in a tablet form factor. I do see it as a 'niche' and I'll defend it in the sense that, just because the iPad outsells it massively, doesn't mean it's a failed concept. I think of it as niche and for real Windows enthusiasts really. The iPad on the other hand is just more universal, easy to use, dumbed down..? sure. But it has its own enthusiasts as well as casual users.
I'm glad both exist, I mean my mum is one of those people who has avoided using technology in the form of a Windows PC or Mac all her life until lately and I'm glad showing her how to use an iPad over a Windows PC every day of the week - and a Mac for that matter, just more to take in. Even though it's things we take for granted. Same with a girl my age (mid 20s) who didn't really care much for technology whatsoever but had an iPhone, way easier to show her how to get things done and literally use that one iCloud sign in to have all her stuff magically on both devices to be able to pick it up and leave it constantly and not need to sit doing any sort of planning or manual syncing... Sure, I love that stuff like a kid loves to mess with play-dough seeing all the ways I can convert, store, organise, edit and mess with my data and software, but you've got to understand that's not the everyperson. The iPad gives them enough utility and easiness to actually re-light that tiny bit of curiosity in 'maybe I can do this with a photo' via a quick search of the app store. Are thye going to join a forum and do extensive Google searches? Nah. But it's all good.
I say this, as a seasoned (now ex) Apple fanboy who has just moved to a dumbed down Note 20 with DeX as his main machine alongside a work issued PC. But my experience of it all, and being iPad only for many periods in the past decade, leads me to believe the above. I think tablets are the future, like Gates and Jobs foreseen. But forever? I think longer down the line.... maybe something like DeX is the future.