Which do you prefer?
Personally, I detest maxis match. I think it looks terrible! It's so chunky and feels... lazy. Alpha is just so much more realistic and that's what I like to see in my game, but it's not for everyone!
If you have no idea what I'm talking about I'll explain a bit (I don't completely know either, though).
Alpha and maxis match are the main textures for cc including hair (including eyebrows), makeup, and skin tone. Maxis match is what the base game is comprised of and some cc out there also uses it. Alpha is exclusively cc.
Here are some screenshots to show what I'm talking about: