Difficult to say without knowing your tastes, attitudes, etc
If you're interested in just sedate driving (comparatively speaking), get the SL.
If you're interested in occasionally (often
? ) letting loose, the SLK.
I thought the SL was a real cool looking sports car (long, sleek) when I was younger and was enamoured of the XKE. Having the '55 for two years now, although I still love the long sleek look the "shortness" of the '55 is what drives (pun intended
) me now. Just finished a five hour drive to Kingston Ont. It was a helluva lot of fun (and comfortable too).
I do get tired on those long drives but only because at the speeds I travel, intense concentration in heavy traffic is required.
Like Jeff said, the SL is a fogey car. Superb in it's own way.
I guess one must ask you:
1)what cars HAVE you had in the past?
2)what do you drive now?
3)what cars do you drool over?
That might elicit more helpful responses.