I have a Cradlepoint PHS300 and noticed something interesting when using mobile data: if I plug my Sierra Wireless USB modem to the PHS300 and connect my laptop via WiFi I get faster speedtest results than if I plug the USB modem directly to my laptop.
This is obviously for the same network, same location (Auckland CBD), around the same time (as in plug to laptop, test, plug to PHS300, text, plug back to laptop, test)...
Also the connection seems to be more reliable.
Interesting.