17-55 ef-s + 24-105, or 24-70 2.8?

[neuroanatomist]

I am toying with the idea of the 24-70 2.8 or perhaps going to primes - w/ the low light performance of the 5dIII it is an interesting question.

I find f/2.8 is often sufficient in 'low' light. I reach for a fast prime when I want thinner DoF.