I've always been one of those people who thought "rear" engine Porsches (aka 911's) were nothing more than a glorified VW. The only Porsches I ever really gave any serious thought to actually buying when they came out, was the 914 back in 1970, and a 944 in 1983.
The Cayman, on the other hand, is one of my favorite Porsche designs of all times. I love the way it looks, and if they weren't so expensive to purchase, and maintain, I'd probably try to figure out a way to buy one.
That being said, in a head to head comparison between a Crossfire SRT, and the Cayman, I'd go for the XF hands down.
Now if I won the Mega Lottery, then I'd probably buy both.