Weight, if you want to take it on and off.
And for leaks. I had a Century Cap on my 94 F250. Fix one leak and two more pop up. It had lots of little windows.
Bought an aluminum A.R.E. for it, really liked it, but it was short. Cab height, the Century was a little taller.
Although if I bought one for my F250 now it would be a fiberglass A.R.E. with the door on the door.
https://www.4are.com/product/walkin/