if you do have lots of cash lying around go for the bmw but if you need to save alittle then cady. if you are into manual style driving then get the bmw. i dont know if the caddy comes in manual but if it only comes semi tranny forget it. smg are not as fun as manuals. altho numbers are what people only look at. you have to remember what type of driver you are. both these cars are seriously fast cars. Ive been in fast cars and you will get into lots of trouble with fast cars. if i were you id get a used m3 for the same price as the caddy or even a used m5 and save some cash. heck 50k might even get an imported r34 skyline. heres something to look at:
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=6212&item=2478869426&rd=1
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=6212&item=2478869426&rd=1