17L also has a lighter trigger pull - since it is a match gun, you would hope that the action would be smoother in addition to lighter. I know that some shooters have tried to acquire the trigger groups to drop into their own Glock but they appear to be unobtainium.
IIRC, they have vents/ports in a slot at the front - essentially a type of compensator.
Don't know what game Glock would say this is for, but they came out when Glock started becoming a hot item in IPSC/USPSA limited class, and were an apparent response to requests for USPSA match guns. At this point in time, red dot scopes were just arriving on the scene _grin_
My guess is that as of today, the 17L is a gun in hunt of a game - the comp puts it in open class, probably makes it illegal for IDPA
I've never seen one. Would like to see how it felt.
Ought to make a killer house gun