They're practically the same thing at this point. It all depends on what you're looking for with either console. What exclusive games appeal to you, the service they offer, and even whatever controller suits you.
I've owned a Xbox One since August 2014. It's been good in some areas, while in others it has yet to impress me. The controller is great and just as good as the 360 controller and the service is still good with the Games for Gold and nice discounts on the store. However, I have yet to be impressed by any exclusives the Xbox One offers. And any exclusive that does interest me can be played on the PC anyway (which is the case most of the time for Xbox exclusives it seems).
But like you say, the Xbox One is getting backwards compatibility which I look forward to. Only downside being it's only a select amount of games you're allowed to play at a time until more are added, so you can't just shove in any game you want and play it. They're likely to make only the most popular games backwards compatible first so if your favorite games are more obscure titles, don't expect to be playing them any time soon. Although games like Red Dead Redemption, Skyrim, and Fallout 3 are among the most demanded so that's a good thing. And if you're looking to get Fallout 4 on console, there is that whole thing with mods coming to Xbox One for the game, although who knows how that will function.
I'm not an 'incredibly enthusiastic fan' so I'm not biased towards either console. I actually plan on getting a PS4 for exclusives like Bloodborne and The Last Guardian. I'd say if you really want the option of backwards compatibility I'd get a Xbox One. Exclusive content wise, the PS4, since in my opinion they seem to have the best exclusive games and not to mention Sony is good at being an ass of a company that likes to rip content out of games available on all platforms to make it exclusive to their console. A ridiculous anti-consumer practice if you ask me.