Flat plate has more surface area. A given it’d perform better as steps. Small misplaced feet can slip and miss the tubes. If steps is what you’re after… All options on the market will have issues with snow/ice pending amount of snowfall. If there is enough ice buildup on steps to interfere with doors, chances are the door handles are frozen long before.
Have the top on ours. It accumulated snow, but nothing I worried about. The trim will accumulate just as much as you'll notice when you take off the side trim for install.