Jeff, no problem. I check new post and happen to see yours. Thought I could help by sharing my experience so far.
Everyone will have a preference on design for different reasons. I started out against having zippers myself. My brother has a custom built metal framed upper door from company in Canada. Covered in same type of material with lot of velcro that he must remove for open trailering or he installs a cover on his rig made for trailering. Time consuming. He also takes the upper door windows off and keeps them in bags ready to install as needed. Will last for years, but he has added additional material around the top and leading edge to make it close off more of the gaps that never seem to be closed off enough in winter for dry powder snow that gets in. He has . It works hours of additional modifications to meet his standards.
I had a few concerns about the zipper at first. I didn't know if it would last or if I even liked it's design. I didn't like drilling holes in new plastic for install of snaps, but it's no big deal. However, those snaps are the only downside. I have had a few pull out of the doors and have yet to fix them, just screw them back in. They will be riveted on before long with some washers on the back side. It's the last thing on my maintenance list before weather is warm enough to start taking snaps off and rolling windows back. It's nice to forget enclosure is even on with windows rolled back and ready for weather at any time. All summer I got caught in rain or just a cold night ride back to camp and it only took seconds to zip windows and go even without using the snaps!
I wanted my enclosure to be easy and require very little upkeep for daily use. The final selling point for me was being able to trailer over 1,000 miles nearly none stop one way at highway speeds on open trailer without removing anything. No additional work every time I loaded or unloaded it. The flopping door top frame design would not have made even a short 100 mile trip without being destroyed IMO. If you have enclosed trailer that will play into anyone's decision and make that a non issue.
The zipper concern is not so bad. It needs some dry lube after washing, but never been an issue when dirty. I don't mud bog my rig. They might be problematic in mud. If they wear out it's something that can be replaced. Just think about your trailering. No matter what enclosure you decide on, know that none of them are perfect. Let your wallet be your guide my friend.