I agree with Whoopsy,
My 2006 911 C4 came with Bridgestone Potenzas and I liked them.
Michelin PS2s came on my last two 911s (2009 Carrera and 2011 Turbo S) and I like them too.  Michelin has the name and the fame in this game.  Each will wear out faster than you'd want them to.  I'd buy the Bridgestones if they were cheaper than the PS2s; if not or close in price, I'd get the Michelins but I can't see how either would be a mistake.
Turbo owners could say this with more veracity but I swear 911 Turbos came with Bridgestones for years.  That's a fairly decent recommendation, from Porsche, I would think.
 


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The price of anything is the amount of life you exchange for it. Henry David Thoreau