One's a lot more expensive than the other, lol.
To be more serious, I've had experiences with the regular SS ML and LB on my Series 0, not the Space Black, but I think it's still applicable. Personally, I really like the classy look of the LB and that was my preferred option, but I really couldn't justify the cost personally. The other thing is that I am currently based in a very humid and hot climate, so my wrist can very easily expand and contract based on if I'm indoors in a well air-conditioned location, or outside, or what have you. Therefore in many instances, my LB either fits fine outdoors (I like to wear it a little loose) and not as well outdoors (tighter than I'd like), or it'd feel fine outdoors and way too loose when indoors. Sure, the links are easy to add and remove, but I don't want to be doing that several times a day.
Eventually I tried the Milanese Loop, but ended up returning that because, again, I like to wear my watches loose and I think the watch sliding up and down on my arm caused irritation. I eventually settled on the Leather Loop, as it still looked dressy and was easy to re-adjust on the fly, similar to the ML.
Fast forward to a month ago and I purchased the new 44m SS with ML. I'm wearing it a bit tighter than I would my Leather Loop, so it doesn't slide around as much, and I've had much better results with far less skin irritation. I really do like the look, and it goes well with my uniform as I wear a suit for work.
tl;dr
Looks: Both look classy, with the Milanese Loop maybe being a bit more modern, with the Link being a bit more classic. I like both, maybe leaning more towards the Link, whereas my girlfriend much prefers the look of the Loop.
Comfort: Loop is more lightweight, whereas the Link will definitely add some heft. Both are comfortable, but I have had instances where both tugged on my arm hair a bit. I'd say they're fairly equal, unless you live in a climate similar to stated above.
Quality: Both are high quality, and you can't really go wrong with either.
Back to the link bracelet. It’s thin, fairly light weight, and the removable links are an ingenious design by Apple. The Milanese loop is significantly more expensive than the Milanese loop, I do think the price tag is justified once you physically get a chance to handle the link bracelet, you will know exactly what I’m talking about.
Oops?