As mentioned the difference is mainly cosmetic -- more important is the make\model and various output ratings of the PSU - If you post the ones you are considering we could give you more specific input as to which choice is better.
EDIT : Just saw your latest post ---- the antec you posted is actually a hybrid modular (most of the cables that are normally used are non-modular (ie. MOBO connectors, etc.) and then the PCI-e and MOLEX connectors are modular so you do have some freedom to only use the connections you use ! It would be a good choice - and yes the 650 comes with 2- 6 pin and also 2 8 pin PCI-e connections so could be used for xfire on 2 5850's