Over the years I've found that there is a big difference between "factory refurb" and "Fred's refurb". Many companies refurbish electronic components and a lot of them do a poor job. The factory job may be better for some of the following reasons: techs trained on one brand and work with the same stuff every day, well defined test proceedures, availability of factory parts, specialized test equipment, a reputation to protect. Theoretically, a factory refurb has undergone much more through testing than units that come off the assembly line. Factory refurbs also often carry the same warranty as new products.
Used product returns are seldom tested by anybody.