The cheaper one is the better choice since they're basically the same.
Both have 64mb cache.
There is no real difference between 64 and 32 mb of cache so if you decide to go with a WD Blue, its still a good choice.
That PSU will be just enough for two 480s. Just don't go crazy with the voltage and run furmark and you'll be just fine.
Cooling wise, you should get decent temps with that setup. Nothing great but definitely a lot better than with the stock cooler.