'97 and '98 are typically the most sought after as it is the last years of the M119 (4-cam 32V) before the M113 when MB introduced the slightly less powerful 24V M113 V8.
Also '97 and '98 were the first years of the better 722.6 trans, HVAC and wiring harnesses.
I've owned a '98 SL500 with the SL2 package now for over 4 years and its been a great car. I also upgraded the suspension (lowered it 2.5") and brakes to the Series 2 V12 (larger) brakes and control arms.
