It's always tough to compare replacement tires. Generally the tires that are replaced are shot and well, aren't at there best. I used to work for Pirelli and nowadays any major brand can produce a top quality performance oriented tire, including TOYO
. I wouldn't say they make the best but at a price point they make a good tire with decent value.
I've been outta the game for a few years so my opinion is only that.
Goodyear makes a decent tire there presence in top level racing has been missed for awhile now but they do manage to stay in the Ultra High Performance game, OEM fitment being the barometer. I remember the GY ZR Gatorback being a very formidable tire in dry traction - absolutly lacking in wet traction despite the proliferate marketing jango saying otherwise. They do now as you know have a very comprehensive and capable line of UHP tires.
Michelin has had the benefit of very recent top level racing experience, Formula 1 (in competition with Bridgestone, a very good situation for the race fan!), WRC, World Superbike and now, this year AMA racing. I currently run either a Michelin or Bridgestone on my motorcycle and BFGoodrich on the truck (Michelin owned).
I quickly googled GY and Mich. to see exactly your choices and I can say this:
The GS-D is a tire that's been around for awhile it has seen OEM fitment, can't recall which model I used to know
. Should be good. It's still around and has probably seen some development since it's introduction. It is a UHP tire and is obviously a very very good dry handling tire, probably a good wet tire too. Just doesn't have the siping for any snow or ice traction. It may say M+S but it doent't mean M+S, it just says it.
The Michelin A/S: A new tire, benefiting from the technology derived during racing. The World Rally Championship experience hopefully went into this tire because it is heavily siped and promises to be all things according to the promo literature. On a high horsepower vehicle I don't see this tire being a good dry performer. It will be an excellent performer in the wet and should have superior performance in snow and ice over the GS-D, given the tread design and advanced compounding.
They are both good tires it's a choice between the old and the new. The Old promises at least dry traction and probably decent wet traction. The New promises it all, dry, wet, and winter a real UHP all-season performer (If it's true it will shatter my preconceptions).
Longevity of tires like this of course should not even be considered.
Sorry I can't recommend a Pirelli tire they seem to have missed the boat and haven't introduced a new tire in some time.
What is the tire going on?