I hold Mercantile as my favorite MSC all around.
The companies (clients) shopped (nice benefits to me for shopping), the employees at Mercantile and the give and take between Mercantile and me.
Don't get me wrong, they have some very involved shops, but they go easier the more shops you do. Also, the auditors are familiar with the people you are shopping, as in "I'm very aware of XYZ employee".
There's a funny thing. Most of the shops I did for them, the people I was evaluating were not the ones I was evaluating the next time. Hmmmmm.
Unfortunately, they don't have shops where I relocated to.