We have done open and closed. Pulled the bikes home from sturgis in pouring rain for about 14 hours in 2010 on an open trailer, never seen a bike so dirty. Bought an enclosed 8x20 with 3 foot v nose last year, only got 3.5 miles per gallon less than with an open trailer. IMHO I would give up the mileage any day for the convenience and comfort of the enclosed trailer. We put all our gear, luggage, coolers, and tools in there as well, and no straps to tie off and worry about. We also like that at night we can park the bike in the trailer so it is out of the weather and more secure. Get what works best for you, but since we are all putting in our 2 cents worth, I say enclosed is the way to go for me. Good luck!!