Wikipedia has a timeline see
https://en.wikipedia.org/wiki/Schuma...acing_Products
The a few difference but the easiest one is the lower chassis:
SWB - Stick Pack (Grey Bumper no front diff)
XL - Same shape as SWb but 20mm longer
XLS - As per the XLS with more option parts included (Silver Wheels)
XL/XLS had a saddle pack option chassis (with 6 cutouts)
Procat - 7 holes for batterys
Bosscat - Lots of options chassis here but the back of the chassis isn't at right angles when it comes in from the batteries and black weave and carbon became an options
If you want Schumacher history one of the better sources is rc10talk which is vintage focused there loads of old articles etc. In addition Daniel had set up a vintage schumacher facebook page where you can ask questions.
Keep meaning todo a post on this with more of the difference that people can help me refine. There lots of Schumacher experts on here that no more than me!