Looks like the side sills on the second car were painted to match the aftermarket stripes...not sure I like the way it looks, and I'm not really big on the cognac interior. My advice is this 1) research the differences between model years 2) decide what features you want (ABS, forged vs. cast internals, 18" vs. 17" wheels, etc.) 3) decide what color(s)/stripes you want 4) find that car. You don't want to be saying "I wish I would have gotten _____" a year from now.
As for these particular cars, if forced induction is in your future, the '99 has forged internals which will stand up to that better. But, I've heard there have also been issues with availability of replacement shocks for the ACR. The '01 has ABS and larger rear calipers, but cast pistons. Find out what work has been done on these cars--have the power steering pump pulley/bracket been changed (prone to failure on Gen II)? There was a frame recall on early GTS's (not sure if it extended to 99's).