Reason being is that this one has it's own chip for storage about 300MHz. See the other one depend on the processor in the router to handle the task. Those tend to be really slower. You could connect WD USB Passport or Element to one and see how slow it would be over the network.
thats a little out of my price range. i guess i could just go the NAS route later on to add network storage. but would u get this for the speed or is their something better for around the same price in your opinion?
None of these routers except the one listed would be the way to go. Yes it's expensive. Choices are buy one for $99 bucks NAS, or turn old PC into NAS Server using FreeNAS.