This is what I do for a quick check of pitchers.

First rating x 2, plus 2nd rating, divide the whole thing by 3.


ex.

7 - 4 guys converts to 6 rating.
4 - 7 guys converts to 5 rating.

Thus a 7-4 guy will produce better stats than a 4-7 guy.

By the way, the best thing to look at is a pitchers OPS vs either a right hander or left hander when deciding who to pitch.