Sounds like it could be the card reader if the XQD card reader can read faster on the same USB3.0 port. I bought the USB3.0 Lexar CF/SD card reader as I didn't have a CF card reader when I bought the D800E. I haven't tested my Sandisk Extreme Pro's with the reader as I usually just import through LR4.3 so it doesn't show me the speed... Also Lexar has a firmware update you can load onto the reader if you get the older one that is only rated to UDMA6, the firmware updates it to support UDMA7:
Now for the older laptop, USB3.0 is backward compatible and will default back to USB2.0 speeds (~20-25mb/s). Just plug the new reader in, load any drivers needed, should be plug and play, and away you go.