From hiking in AZ and Utah, I have found that both ways will work. As always there is a But..............
Nylon shorts on open trails works well........but when the trail becomes more dense, the bushes will have needles that will scratch up our legs, the dried grass will stick to your socks ( dirty girl gaitors will solve that ).
After reading a post from a triple crowner, I did a 50 miler in long sleeve shirt and light, baggy, full length pants. It also worked well. Didn't use or need any sunscreen. Kept much cleaner. Socks stayed cleaner. Last two days were in the 90's and did not feel that the pants were a negative.
I would suggest that you give a pair of baggy convertible pants a try.
Either way will work.