A disk's cutting ability is determined almost entirely by weight per blade. You can fine-tune the cutting with the blade angle but no amount of angle will make up for a lack of weight. The bearing style will only effect how much maintenance is required and how hard it pulls - sealed bearings are better on both counts.
I can tell you from first-hand experience that lightweight 3-point disks just don't work well in hard ground or in heavy trash. (Mine was a 500-lb 5-ft model.)