As someone who has had five or six Apple laptops since they went Intel, and whom also owns a SP4 and thinks the Surface Laptop is the sexiest laptop on the market, I feel fair and balanced to provide a suggestion.
Let's first start with what should be obvious: they're both great devices. Arguably, you're comparing the two best laptops on the market, period.
It truly just boils down to the form factor and OS you prefer. Obviously, pen and touch support - and a tablet form factor - can be supremely beneficial in certain use cases and give the nod to the SP. However, as a laptop - and always a laptop - the MBP is unquestionably better - it's gonna have much stronger "lapability" and it's more usable on small workspaces (like a plane's seat tray).
OS is truly preference. You say you're into gaming - but the SP has integrated graphics and isn't going to be playing anything other than old Source games or indies at respectable framerates/settings. The 15" MBP offers a 560 GPU - which is far from even "good," but it can handle some more modern stuff like LoL, Overwatch, etc at 1080p low/medium settings.
Build quality is great on both, but the MBP's screen is a good bit better, IMO. Better color accuracy once I calibrated both; and definitely brighter (500+ nits vs below 400). MBP has better touchpad, too. I think the MBP feels more solid. However, the SP is lighter, which is an advantage, and both keyboards are merely okay - so wash, there.
I got the 15" 2017 MBP mainly because I wanted the best 15" screen I could find, which I firmly believe is the one Apple offers. That, and I just much more prefer OSX on mobile devices - things like PowerNap, sleep, battery longevity, trackpad functionality, and multi-full screen make it more pleasurable on the road... but most of that is subjective. I also wanted a quad core CPU that isn't as held back by voltage reqs - which really, MS offers nothing in that space. That may not be as important to you, though.
Ultimately, I think they're both great machines. If you want the tablet-y formfactor, touch/pen support, or a built-in USB-A port; well, Surface is the only way to go. But if none of those things matter, and you're okay bumping up to a 15" - I think the MBP is the much better device.
If you're only considering a 13" MBP, though; then arguably the decision is much tighter and I'd probably base it entirely on OS preference.
FINAL NOTE: Fwiw, I actually despise my wife's SP4. Literally nothing but sleep, wifi, and firmware problems. 10% of the time it should be fully charged it's dead as a fucking doornail. Awful. Terrible, terrible experience and I wouldn't recommend a SP4 to anyone. HOWEVER, supposedly the newest SP does not have these issues; and so the above arguments assume you'd be selecting that.
