I am a Windows guy, but have worked with macs in the past as well. I must say, Mac is much easier if you are just starting out and have no preference.
Most DAWs will work either way. Interfaces work both ways (some have both USB & Firewire). Thunderbolt, BTW, has had a lot of issues with Windows based machines. Firewire, as well has problems unless you get a certified TI card. Best in the Windows environment to stick to USB/PCIe. Mac can use all if they have the ports (some no longer have USB)
Your external equipment, of course, will not be affected.
So, unless you're intent on going with Garage Band or Logic Pro you can use a Windows PC and get the flexibility (and the headaches) of the open architecture. You are likely to spend less, but you might get lesser quality, depending on the builder. Most of us have dedicated PCs for recording and keep them away from internet (for the most part) so we can control upgrades and other such nonsense that slow or corrupt our systems.
Unless you are looking at FLStudio, you can use a Mac and get the structured support of Apple's proprietary hardware and (mostly) trouble free upgrade paths. You may spend a little more, but in the long run, it might be worth a few less headaches.
Happy Recording
Like BroKen_H, I, too, am mostly a Windows guy, but have used Mac almost exclusively for tracking.
In fact, quite a number of years ago I spent an incredible amount of money on a Mac Pro (that's the tower, not Macbook Pro) because, after years of research I had concluded that there were (then) so many conflicts in the Windows environment that the Mac environment sounded simpler.
I was right, and wrong.
Right in the longer run, but at the time that I bought my Mac (around 2007) the chipset was having problems with some audio interfaces, and the expensive (firewire) audio interface that I bought (Presonus Firestudio) would suddenly stop working at times when tracking (loved the preamps, though).
I also had problems getting used to the Mac OS - I wanted more control than one is afforded in OS X (I have been using computers since before DOS!), and also was frustrated at how illogical things are (as they are in Windows, too, but I was used to Windows).
Now, though, I am happy.
I think that the quality of audio interfaces has improved, so I have no issues with the five or so I now own (they are all USB).
I do love GarageBand for its simplicity, and one can do a surprising amount with it (but the current version seems to have oversimplified things, so I use the previous version). Also, GB comes with quite a few loops, and has the requisite FX's, so making it a fairly complete DAW (although nowhere near as comprehensive or 'deep' as others).
And there are, of course, other DAWs which are available for Windows and OSX.
For example, Reaper looks and functions the same in both platforms, and can be used on a trial basis until you decide that you want to contribute financially to its developers (unfortunately, there are very few effects, and no loops so you would have to find and download those separately).
There are some excellent, very cheap audio interfaces - specifically, the Steinberg UR22 and Roland Tri-Capture (both of which I bought - for different reasons - recently - see my recent posts about these if you are interested).
The one word of caution I would give is to do your research (like you have done by posting your question in this thread).
Because I bought the then top-of-the-line Mac, I do not know, for example, how current all-in-one Macs differ in performance (i.e., whether they can cope as well or better, or worse, with latency as my computer).
Good luck with your search and decision and let us know what you decide.
gvdv