A blued gun is better for accurizing, and a better target gun. The metal is "smoother" (Stainless has high/low places) and can be made to closer tolerences (Though stock guns rarely are)
Stainless very low maintainance, nice looking and will keep it's finish looking nice longer. Also Stainless steel is usually "harder" that blued (As I understand things)
My opinion, Stainless is what I carry, very reliable, doesn't rust, and if I forget to clean it (which of course I NEVER do
) It still functions perfectly.
I have a blued gun for target competitions, that has been accurized (Of course) and is very accurate, though a little less tolerent to me being an ass with it
All in all, I prefer stainless do it's rugged build and it's longer life.