Question What's the difference in PSU efficiency/which PSU to choose for X58

[hubx]

Hello. Is it more efficient to have PSU with more Watts if they cost the same? Or such a small difference it won't matter? I tried to use power supply calculator, but I don't get why it tells me to get 850 when my Maximum Load was 617W, and safe margin ~680W. Shouldn't 750W be enough?

My setup:
Mobo: P6T Deluxe V2
CPU: xeon x5675 @ ~4500Mhz
CPU cooling: Antec Mercury m240 AIO
GPU: RX 580, let's say ~1450MHz/2250MHZ
16GB DDR3

PSUs I can choose that cost the same amount:

1. EVGA SuperNova G2 750W GOLD+ with 9 years of warranty.
2. EVGA SuperNova G2 850W GOLD+ with 3 years of warranty.

6 more years of warranty are pretty relevant I think that's why I can't decide and need your help. Thanks

 

[Dark Lord of Tech]

EVGA SuperNova G2 750W GOLD+ with 9 years of warranty.
Is plenty of power.

A very very good PSU.