A 12" is as big as I'd ever use. I prefer an 8" -- easier to handle, and big enough for most anything I can anticipate. A friend of mine bought Bert's 13", but that's just way too large for my needs. (and I couldn't afford it) So his 8" became available so I snatched up that one.
p.s. the 13" weighs just north of 250lbs.