The S is the road legal model and the E is the off road model.
It's an S if it has the big tail light & turn signals hanging down in back. Also an S if it has a speedometer and indicator lights for neutral, high beam, and temperature. The S will also have a steering lock on the right side of the steerer head. I believe the carb is a Mikuni, and it runs on regular gas. Sprockets are 15/44 stock.
The E has a larger exhaust header, an odometer only, no neutral indicator light, a small LED tail light but no brake light, a Klein FCR carb (unless it's a new California model). It also has higher compression (requires premium fuel), slightly higher rev limiter, 14/47 sprockets, a little more HP, and is about 25-30 lbs lighter than the S.