Watch out for uneducated saleperson. Do your homework. I thought I did mine, but relied on the salesman too much. He was not up to speed on the details. I chose the S, but found I really only needed to ride on the street once in awhile. Here in Idaho, U.S. registering the E for street is not a problem. Get the details from your local motor vehicle dept in writing.
Here are some basic differences between the two models.
S comes with street tires, not worth much for offroad use, the E has knobbies.
The new models have the same suspension. No cush any longer, it added weight, and price to manufacturing.
The gear box ratios are the same. The E does come with different sprockets for more lower end power, the S is geared for faster speeds. I changed my sprockets front and rear long ago for more hill power since I don't ride much faster than 60 mph for extended periods.
The S has a Mikuni CV carb, (constant volume), the E has the Keihin FCR w/ accelerator pump for quicker throttle response.
The E has a thinner head gasket, this increases compression.
The S comes with a vacuum operated gas cock valve. I have had to replace this twice at $ 70.00 U.S. each. The first one gummed up from me not draining all the fuel for the winter, the second one started leaking at the valve body gasket. No rebuild parts are available. I ordered the standard valve that comes with the E today. Am converting. Tired of problems. Kind of screwed up my hunting trip last week due to the valve body leaking fuel all over. Use only premium fuel. Winterize properly.
They have different cams. The E has approximately 6 hp more than the S.
The E has rim locks for off road action to prevent tire to wheel spin, the S does not.
Plastic fuel tank for the E, metal for the S. I installed a larger capacity plastic desert tank right after I realized that plastic handles trauma a little better than metal.
If I had to do it over again I would get the E over the S any day. The extra power, lighter weight, and more durable for off road. Hope this helps.