I have no experience with the Michelins, but about those Pirellis:
A few years ago my mother's 94 Grand Marquis needed tires, & I happened to spot a ridiculously low price on some Pirelli 400 WW's- the bad news, available in only 2 sizes. The good news, one size was 215/70/15. I took off, went 30 miles to Longview & got a set mounted & balanced, out the door, all for less than $200. They were supposed to be blems, I could never see what the blemish was on them. The car drove & handled better than it ever had before, grip in the rain was *excellent*, & they continued like this up until they wore out, at something like ~25,000 miles. Even then, everything but wet grip was still very good-exc. So, Pirelli 400's on the big Merc: Upside, handling wet or dry, braking, drove beautifully. I can't speak for ice & snow. Downside: they wore out kinda quick. I now have some high-treadwear-# BFG-made Reguls on her car. They're an OK middle of the road S-rated tire, but they don't inspire confidence like those Pirellis did.