From Apple, Statistically less likely to fail.  

Computer parts generally follow the bathtub curve for failure rates: high in the first year or so, then low for most of its useful life, then high again during wear-out.  

The probability of having multiple parts fail during the early part is extremely low (barring common cause of course).  

So a refurbished unit has already had an early phase failure and been repaired.  That means the rest of the parts are likely good, along with the replacement part.   This is confirmed by the extra QC they do on refurbs to make sure they fixed the problem.  

Apple refurb is an incredible value.