FE/FC 2016 FE350S vs FE501S?

I was dealing with the same problem . Former local pro motorcrosser turned dualsport off-road rider. I ended up going with the 350 as I've always had more fun on the smaller bore bikes. I'm 5-11" 185 this bike does not kick in hard until mid range to high-end. Just drop the counter sprocket one tooth, change the endcap or put a slip on exhaust then you can get some good grunt out of the bottom that is your thing. Cruises comfortably on the asphalt at a little over 60 and can twist it up to 80 no problem. Get rid of the stock tires if you plan on ridding some street that front knobby is a deathtrap. I Put a set of the IRC TR8 battle rally tires on the Ride love them !