Other. I use a number line, numbers assigned to stats as the player wishes. I could have a step of 1 (11, 12, 13, 14, 15, 16), or 2 (7, 9, 11, 13, 15, 17), or 1.5 (8, 10, 11, 13, 14, 16), or whatever.
I also don't like super-scores to start with, so players playing races with stat adjustments must ask before placing their highest numbers where they'll be increased. E.g. a half-orc couldn't put his highest number in Str. At higher levels, this gets relaxed. The reason for this is that a high stat is vastly more significant than a low stat.