I do not think the type of bearing a disc has will have a lot to do with how well it will cut. I do think a disc with roller bearings will pull much easier and you are not having to lube the disc all the time.
I think the weight of a disc, (heavier) the better and having slotted blades will make a disc cut better.
I have an Altas 300 6ft. Disc, it does an ok job as I would call it a med weight disc. But it has the old type bearings that have to be greased.