The belt size can be very handy, but I've found that with a disc, bigger is always better unless you really are just doing model sized stuff.
FIL gave me an old Delta combo, wider belt but same 6" disc. I really kinda hate it, universal motor screaming away.
The Rikon looks to have an induction motor which would be a big plus as far as noise. DC is always a +.
Another thing I think is a "must" is to have extra disc platens. Swapping grits is something that is handy. PSA discs are nice in that you get a very flat surface, but H&L solves the grit swapping issues.
Tools of this size class are the mainstay of several manufactures (Wen, HF, Grizzly, Skill, etc.) so you might find some magazine reviews that cover a range of brands.