I used a lower quality Craftsman (likely from the early 80's) in my Grandpa's shop many years ago, I remember being unimpressed by not only the quality of the machine but the capacity too, particularly the small disc.  I have a 2x48 sander I use a little for wood and a lot for metal.  For bigger projects, I also have a 6x48 belt/12" disc sander unit and I use that 12" disc quite a bit.  I'm certain the quality of that Rikon is better than the old Craftsman but the capacity would still be a problem for me.  FWIW, I'm actively looking for a 24" disc sander as I use mine enough to know that more capacity is always a good thing.