Not to be a dick, but this is backwards. Hardware differences (apparently Flack didn't mean what I thought he did, but whatever) make a hell of a lot more difference in programming than what color the shell is.
For example, there was some frantic work done on the CD-i to make models work correctly with sound (don't recall the details exactly but it's on the 'net). That ended up having an impact for all future programs written on the system.
Everything else is just kind of aesthetic. To me, it's most interesting to find the Neo Geo AES with the best capability for video, or the Genesis with the best sound, and so on. 'course, YMMV.
Likewise for the PlayStation CD-ROM read speed. Now, I don't think any PlayStation units read at different speeds than others, but if it were true, people would be searching out "faster" PlayStations. It would make a small but noticeable impact on gameplay and enjoyment.