Two now
I actually think both look quite nice, but from a 90's supercar collect ability standpoint popups will be a strong factor.
While there are 2,886 US model 1991s, that is still a very small number in collector terms and the number that haven't been chopped up, abused and simply driven is very rare. The 2002+ vehicles in general have remained fairly pristine due to their high price tag (relatively) and limited numbers. So the number of "Condition 1" collector type 1991s probably won't lag that far behind the number of pristine 2002+ models even though only 825 US model of them.
The 98 you are referring to is slightly different as it didn't start life as a fixed light version and get switched to a pop-up. It just got put back the way it was more or less.