My favorite was the C plate until I got the F. I pretty much always use the F now. I got it out of curiosity expecting it to be way too aggressive to be practical but it is the smoothest plate of them all for me. Because I can pull it around my face with zero pressure, I hardly ever get nicks or razor burn using it and because it is so efficient I can get BBS with 2 passes and a little touch up.
What I've read is that all the plates below F have some degree of negative blade exposure meaning some pressure would be needed to get the blade flush against your skin. The F apparently has neutral blade exposure allowing the whiskers to be cut right at skin level without the need for any pressure. I don't know if the whole blade exposure thing is a load of BS but it works for me!