I've just run both of these for the Nurburgring Lap Times Leaderboard (link in my sig).
I'd run the '08 previously and thought it was quite a nice car to drive... so I decided to test them back to back.
They are both a bit understeery on turn in, but as long as you manage the entry speed carefully, they have a lovely mid corner balance and plenty of traction on the exits. The '08 has a slightly better balance than the '05 (less understeer, changes direction better), but the '05 weighs 140kg less, and is a decent amount faster in a straight line.
Both are stupidly fast at the 'Ring for a big saloon car. With just an oil change, but otherwise completely standard I ran;
'08 7'24.746
'05 7'21.993
Neither lap was anywhere near perfect.