Regarding the Boxster rollbar issue, though you haven't mentioned track days - many, perhaps most, track events in the Northeast permit the Boxster to run in any group with the stock rollbar, provided the top of your helmet doesn't extend past a line drawn from the top of the windshield frame to the top of the rollbar (the "broomstick" rule. I've seen an actual broom used at Lime Rock). An aftermarket rollbar extension is available, and some folks have even put in lower seats.(I'm a track instructor and a PCA tech inspector, and run with a number of the different clubs). I have lots of track days in both cars, they're both great. The S version of the Boxster is a potent car, not a poseur in the least.
In Rochester you'll need a second set of wheels with snow tires for either (used Boxster wheels are easily found at reasonable prices, I don't have any info as to M3 wheels).
For every day use, they're apples and oranges. You just need to evaluate your needs. The comments on ride quality are correct, the M3 is very stiff for daily use.
FWIW, I considered a similar vintage M3 for my daily driver, but after driving the S4 decided the Audi was a much more pleasing year-round performance car (and great on the track - provided it's a rainy day...)
