I need to put some portable rollers in front/behind various tools for longer pieces of wood. I have seen many cheap ones that are just a single roller (like a rolling pin for baking) on an adjustable stand. I also have a bunch of bearing(?) type rollers. These are steel boxes with about 7 balls sticking up through the top.

The bearing type will let me move the wood sidewards as well as forward and backward (like the roller stands).

My question is what is the drawback of using the bearing type? They have less surface area touching the wood. Is this good or bad. Will I get "dents" or groves in the wood as it passes over the balls? How about affect on any parts that may be finished/sanded? Do the rollers cause less damage to the material?