MX Browns - My current favorite, but not quite perfect. I like the low force, and the subtle tactility is enough to provide a pleasant typing experience without being in your face. They're excellent for gaming; the tactile bump lets you hover right above the actuation point, so you only have to move your finger about 0.5mm to actuate the key, and the force is very low.
However, due to their subtlety they're also rather boring. Additionally, they feel different from keyboard to keyboard. My favorites are the ones on my MX8000, with the SPOS a close second. Also, they unfortunately lose their tactility after a few years of use, as witnessed by my first MX brown keyboard, an MX11800 that felt nearly linear. But for the first 3-5 years of use, any decent MX brown keyboard will rank up with my favorites.
MX Blues - These are probably my second favorite. They're anything but boring; the tactility is very crisp and snappy, and they're a pure joy to type on. However, they have two flaws. First, they're extremely loud in comparison to other MX switches, enough so that they bother me even wearing headphones. Second, I have trouble gaming on them; I feel like they jam up on me and I can't double tap or switch keys quickly on them. I'm also worried about their fragility; they're a complicated mechanism, and jam easily.
MX Blacks - I don't have a lot of experience with blacks, but my overall impression of them is one of ambivalence. They're not phenomenally good for typing, and actually feel slightly mushy if you don't bottom out (which doing so will tire your fingers). I don't see any advantage over MX browns for gaming; a disadvantage actually, since there's no tactile bump to help with the hovering technique. Overall I think I could live with MX blacks, but they're nothing special.
MX Reds - Earlier I mentioned that MX browns lose their tactility. When browns lose their tactility, they turn into MX reds. Almost literally. A brown switch will become linear and slightly lighter in force after about 5 years of use, and at that point there isn't much difference between them and MX reds. MX reds are decent, but really are even more boring than browns, without the tactility. Again, I could live with MX reds, but I wouldn't go out of my way to acquire them.
MX Clears - Before I tried them, I believed that clears would feel just like browns, but heavier. I was wrong. If anything, MX clears remind me of Alps switches, with a frictiony, unpleasant tactile bump. MX clears feel more like a rubber dome than any other Cherry MX switch, and it's a mediocre rubber dome at that. The only benefit is that they don't have a mushy landing like domes do.