What's the difference? Obviously one has more power but what will that do? ( Noob question I know XD haha)
Well, first of all it's not really "twice as much power" (technically[i.e. you can't pile on the power to your CPU{though I'm not sure it's possible to dump that many amps on the CPU anyhow}. It is double the power for all other components though.]) It means it is two PSUs capable of 38ams at 12 volts in one box there, instead of just one with modular cables so you only need to plug in what you need.
Pros of that Antec: Safer power, able to run more hardware
Cons: cable management, power stability
questionables: it's green. Personal aesthetics vs functionality choice there for you
Pros of the Rosewill: no difference in power fluctuation (due to single 12v rail, not having differences of power on the lines[which you would never notice unless you did something really noobish like mix-and-match PCI power connectors across 12v rails... which you wouldn't do on this small of a PSU anyhow].) Modular so cable management is easier, larger fan so quieter.
Cons: Can't run as much hardware (still more than what you need though [unless you're going to seriously OC]. But if you consider xfire the Antec will be a much better option)
Simple answer; Both will do what you need right now, if you are going to OC or Xfire go with the antec 100%, otherwise I might still consider the Rosewill for the quieter fan and modular wires.