Personally I'd go with the Boxster S because I NEED to have a convertible.
The only problem is that extra torque and HP of the 911 could be addictive....But in the end it would piss me off too much to see other drivers lower the top on a nice sunny day while I lay inside a ''coffin'' with the AC on....
Top down motoring is just so orgasmic....
If I didn't care for the top down factor I would say 911 S in a flash.
Now with a 911 S Cabriolet, that's a different story, and a different price tag
Solution?
Get a slighly used 2007 Boxster S for 50 000$. 300HP in a sub-3000 pound mid-engine roadster is nirvana to me...
Keep in mind I've only driven a 2003 911, not a 2005+ 911 S!