is run by Miller's, and does not require the same minimums. I had been using whcc before MPIX started, and have been happy enough that a switch hasn't been warranted. They seem pretty close in terms of prices and products though, and I know several colleagues that have nothning but good things to say about MPIX. WHCC customer service has been terrific, I've had very few problems/mixups and they've alwasy handled them quickly.
I may try MPIX for the B&W paper option, I'd be curious to see how that compares to B&W I've been getting on color papers from WHCC. (B&W on metallic paper looks really great for a lot of subjects).
WHCC sent out a note this year saying they are going to also start offering inkjet prints on a variety of papers which would be a nice option as well.