Apple used to have great professional-level software for photography called "Aperture" but they abandoned that market to Adobe. So if you do buy a Mac it s so that you can run some 3rd party software on it. CHOSE THAT SOFTWARE FIRST. Apple's "photos" is very limited, even for casual iPhone-using snapshooters.
The reason to buy a Mac is that it runs the software you like.
There are a number of different questions and use cases in this thread - from those with more advanced photo needs to what seems like people who haven't settle on anything. That caveat aside, I'd approach parts of this differently depending on the user. Not trying to disagree with anything, just a different thought process/approach - for what it's worth.
Also note: a lot of this won't apply to those that already have massive libraries and workflows - that gets tricky quickly. Switching your main editing suite and workflow is
painful.
-I agree that if you must have a certain suite of software, and it only runs on one platform - well, there it is, use that platform, you don't have much choice. If this is you, you probably know it already anyway and don't need advice.
-But for a lot of users (me anyway): I'd say use the platform you like and enjoy. Most of the mac users I know will search for mac software to meet their needs rather than considering switching platforms. (May be different for those pros or others for whom digital darkroom is main use - for me it's only one of several core uses)
-Fortunately these days, several (most?) of the main photography suites and programs - the flagships - run on Mac and Windows. So up to the user.
-There is spotty / uneven support from the camera manufacturers sometimes on mac for their own 'camera support software' like DPP, but - unfair generalization perhaps - their software sucks anyways; don't use it unless you know why you're using it; almost noone has to use it.
-For a beginner or modest use, Photos is not bad at all - way better than it's given credit. Over time they've improved it and integrated more of the heart of Aperture* (which I adored and I'm still livid apple dropped it). To be clear: I couldn't use Photos for my main stuff but ... it's decent. It's usable, it's gotten better, and could serve someone at a basic level pretty well. I'd have no hesitation recommending someone use Photos while they
start with photo editing on a mac and until they've had a chance to try other editing programs and figure out what works for them. (And if it turns out Photos meets their needs, all the better). [Please don't @ me with things missing/wrong in Photos - I'm not claiming it's great or has all the features - but it is accessible and serviceable and included with the MacOS.]
*I'm mostly using lightroom now but aperture's levels was/is brilliant as the single best intuitive way to fix most photos quickly, and Photos has the closest I've seen of a Levels implementation as simple as Aperture.
