Originally Posted by NexusRed
OP will get faster access times but he's still limited to the bandwidth of USB 3.0. Just because the warehouse can find and package your item in seconds doesn't mean the truck will get it any faster.
If he wants to fully enjoy the speed of an SSD, it needs to be connected to the onboard SATA III controller and not through USB.
USB3.0 will basically match SATA II speeds.
If his motherboard supports SATA III then he probably has an eSATA connection there somewhere which will allow him to use an SSD externally and still get the full speed of an internal SATA III drive. Off the top of my head I can't think of any motherboards that support SATA III and doesn't have an eSATA connection. He may need to buy an eSATA backplate adapter to mount to his case if it doesn't have the port built in, but the motherboard should support it. Single port eSATA backplates only cost around $5.
If his motherboard doesn't support SATA III then he may as well use USB3.0. The speeds will be virtually identical to SATA II, provided he is running the drive as the only device on his USB3.0 channel.