Kingriz1
If you do search I think you'll find more info than you can use. I know there's a couple of in depth posts on this forum.
Ride what you got! 125's are competitive in both, BUT you might need to be street "legal" for enduros, and you moght need a spark arrestor,... Check your local organizing club. As far as I know you have to belong to a club to ride either, and AMA if it is AMA sanctioned.
Try to go to one of each and look around. I've ridden both but now prefer H/S only because of the tracks we ride. Here in the FL sand the enduros trails seem to get really beat up (can you say whoops), I think because the trails are used a lot, not just for the enduro. We get whoops at the H/S's also but they don't seem so bad or as endless. Because of the shorter loops the trails are often new, at least for the Sat. riders.
Body conditioning is also a factor - enduros can be 4 to 6 hours, H/S's are 2 hours or less.