Might depend on the PC case you have (or getting), & the system you need to power.
Remember the Antec CP-850W is guaranteed to fit in only 3 cases at present - the Antec 1200 / P183 / P193 cases.
The Antec has 4x dedicated PCI-E connectors, which can comfortably run 2x high-end graphics cards. While the Be Quiet only 2x connectors, which can comfortably run only 1x high-end graphics card.
Where will you be buying it from btw? There appears to be a £10 difference between the two (click here & click here) - not £30 as you say. G