4D M3 - Nice.
I liked my E92 Here's me on Tail of the Dragon one year:
Attachment 34612
I'd say ownership costs are "less" for the Porsche. At least for my sample of one, ymmv greatly of course.
The 981 Cayman, for whatever reason, seems to not have, really, any systemic issues, at least from browsing the P-car forums (Rennlist, Planet 9, etc.) The most common issues are door panel warping (not on mine yet), headliner droop (not mine, either; although my A-pillar seems sketchy, see above a few dozen posts - it's been fine since I tucked it back.) Oh and the headlights polymer seems to craze over time.