The HD4890 will have the performance edge over the HD5770 but at the expensive of higher power consumption and more noise.
I would look at getting the His card
TBH. The card does need one 6 pin PCI-E power connector and one 8 pin PCI-E power connector though. I think power adaptors do come with the card though.
Unlike other comparable ATI and Nvidia cards the HD5770 only needs one 6pin PCI-E power connector.
I would definitely check what PSU your friend has in their PC and what connectors it has first.
Also it maybe worth looking if EVGA will replace the card too. I would check the warranty as he could end up with a better card if they will replace it.