[Jeph]

Ha, I have a Boxster and my room mate has an M3 (E46 though). Welcome to the forum.

Just to clarify, the years you specified on the Boxster spans 2 generations. 2005 is the 987 and 2004 and before are 986s.

I can't speak directly to the question at hand seeing as how I haven't owned a BMW, but I have driven both E36 & E46 M3s. From my observations, Porsches are just tighter cars. Your car is a Dinan, so I'm thinking you may presently have more power. But to me, the biggest difference between these 2 cars is finesse. Porsche has that mastered in my opinion and finesse never gets old.

I know it's not an issue for you, but I think space is something you would miss the most. On a recent trip I had to put a towel in the trunk because there wasn't enough room in the car for it in addition to another passenger. A TOWEL!

Based on my room mate's experience, you'll spend less on maintenance with the Porsche.

Are you considering other cars as well?