I don't put a lot of stock in the training the MBA provides, but I do think on the whole MBA grads tend to be better hires than non-MBA grads. For recent grads, all things being equal, I'd take the MBA-grad.
Is it that extra year or two of age? Possibly... Is it the personality type of someone driven to get an MBA in the first place? Possibly... Is it the training and networking and exposure to other like-minded individuals via group projects? Possibly...