I'm picking up my S550 Coupe tomorrow, but I STRONGLY considered the LC 500 first. Both would be used low (like new) miles, but ultimately you get more bang for the buck with the S550. More technology, more luxury, and while both of back seats the Lexus definitely has a smaller back seat. I think the car is bad ***, but I've only seen 3 in person and they're much smaller looking in person. The exterior is nice, but the interior...I don't know. No one makes an interior like Mercedes. Especially like they do on their CL > S550 Coupes. My CL was my favorite car, and I typically get a new toy every 2 years. I still regret giving that car up, but I'm back. The S Coupe which I wasn't in love with the exterior originally it's growing on me. To me the S550 Coupe looks too much like the other MB if you don't look closely. Obviously when you step in you'll know it's not any of the other MBs but it's lost its unique look. The CL didn't look like any other car in the lineup.
I'm way off topic, I like the LC500 for it's exterior. But I'm not thrilled with the size, or interior. It has no where near the features as the S.