The D700 is better.
Professional use DSLR cameras do not have video capability. Video in a DSLR is marketed to the person with very infrequent video needs; vacations, baby's first steps, and the like.
Anyone with a need for video will want a dedicated video camera unit.
And it always will be...the video capable DSLR will never replace video cameras...but they are becoming an important tool for many professionals. As always, any professional will use the tools they feel best fits into their individual style.
OK, the real issue is which camera should he buy for his brother that plans on studying photography. If your brother plans on attending an actual school for photography most schools have equipment they loan students for assignments. This is normally top of the line still and video equipment. Plus, student photographers first learn in manual mode so all the other features of either are a moot point. So, buying the D700 that goes for twice the price of a D5000 seems a little overboard considering the above. Plus remember, when shooting with full-frame cameras such as the D700, you really need the best quality lenses in order to take advantage of the edge-to-edge sharpness gained from the full frame format. My bet would be on the D5000 or even the D3000.
OK, the real issue is which camera should he buy for his brother that plans on studying photography. If your brother plans on attending an actual school for photography most schools have equipment they loan students for assignments. This is normally top of the line still and video equipment. Plus, student photographers first learn in manual mode so all the other features of either are a moot point. So, buying the D700 that goes for twice the price of a D5000 seems a little overboard considering the above. Plus remember, when shooting with full-frame cameras such as the D700, you really need the best quality lenses in order to take advantage of the edge-to-edge sharpness gained from the full frame format. My bet would be on the D5000 or even the D3000.