If you're okay with both colours, then I recommend the red. It is darker than the blue so it won't show dirt as easily.
I totally get what you mean about black bags. I'm trying to avoid getting them too as I have so many already.
That is the major reason i am considering red. I like this in red, the bag looks Christmasy in red. However, I am usually not a red bag person. Is the lambskin super delicate? I own Chanel lambskin and I am okay with the wear and tear on that one.