1996-2000 320 or 500sl?

[anc4]

my wife just drove a 98 500sl w/ 32k miles, sport version and loved it, before i pull the trigger, should i look at a 99? i heard that the engines were modified in 99. also, a 320sl would give here better gas mileage, but at what sacrifice in performance? any imput would greatly be appreciated.
happy new yr to all!!