The Antec is cheaper, both seasonic internals apparently, same efficiency, wouldn't be surprised if they are the same inside. White one is modular which is alright but not really needed since they both don't have that many connector's to make modular. I think the non modular would look tidier because the cables are all together not spread out. The fan look's better to me on the Antec.
That PSU calculator isn't very realistic, but useful still as it doesn't hurt to get a more powerful PSU than you need. According to the calculator I need over 600W but my PC at absolute 100% GPU CPU load is 260W.
CiT is cheap nasty from that shop that charges you at least double the online price. They tried to sell me a 650W PSU the other day, after looking at the actual unit it didn't weigh much and it wasn't even painted or sleeved. £50, bargain. CiT one also had no mention of a warranty on it.