I really like my aluminum topper with side window doors. Now that I have had one with the side doors I am never going back to anything else. I really like the extra lockable space and the side
windows are large enough not to obstruct my rear views. I have thought about a cover on occasion but have been spoiled by too many years with a topper and can't see giving up the space. I actually have a false floor built in the back of the truck (just clears the wheel wells) that gear (folding camp table, chairs, etc.) slides under and the height makes it easy to reach everything else thrown on top.