@belgianfr The first one has the Cat 4 modem, the second has the Cat 6 modem. Second one should theoretically be able to support better download speeds but a lot will depend on your telco and what they support.
Same holds for the X750 which supports the Cat 4 or Cat 6 mini-pci LTE modem card.
Unless you need the battery for mobility I’d suggest the X750.