Suspension is much much better on the 500 than the 300. I had a 300CE sportline a few years ago. The 500 is in a different league, although it still feels heavy. (although my other car is a race spec Elise, so it's all relative! ).
V12... I prefer the more brutal look of the pre facelift model. Also the 91/92 500E had a more powerful engine and better front shocks.
I like the stock wheels aswell... much better for the surprise factor. I bought the 500 as I was fed up with the world and their uncle trying to race me in the Elise.