lets say with a rig of 6 7970's just as an example

2x 750 watt gold psus = 200 + 1x500 watt psu for $50 = 250$

or

2x 1050 watt gold = 440$

Other than having less parts is there really a benefit to choosing the latter?  Is having more PSU's less power efficient?

I am thinking in terms of multiple rigs.  So saving 190 per rig can really add up.