I strongly recommend k/9 over straight K's for pitchers, and I would say atleast 20-23 min innings pitched.
On terms of cats we usually use 13...
7 for hitting
R, HR, RBI, Ks, AVG, OPS, SB
and 6 for pitching
W, L, SV, ERA, WHIP, K/9.
Some managers prefer k/b ratio over WHIP and walks instead of OPS. To each its own.