Can anyone tell me what GMLAN & MS-CAN are?

I would like to purchase a bluetooth OBD adapter for my fiance, who's an auto mechanic, (link (http://www.amazon.com/gp/product/B00H9S71LW/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=ATVPDKIKX0DER)) and the company that makes the specific one I'm looking at also makes a more expensive one and the only difference between the expensive adapter and the cheaper one is that the expensive one says that it supports Single-Wire CAN (GMLAN) & Ford Medium-Speed CAN (MS-CAN). What is that? Should I suck it up and get the more expensive one? Will it make that much of a difference?