Onboard m2 slot or pcie m2 expantion card? which is faster?

Mini PCIE slot use on XG 125 - Discussions pcie expansion slot The full-height PCIe adapter slots are located on the left side of the expansion node and are numbered 1 and 2 pcie x4 in x16 slot PCI Express , officially abbreviated as PCIe or PCI-e, is a high-speed serial computer expansion bus standard,

pcie 50 x16 slot LaCie makes several expansion cards that use this connector The difference between the normal 32 bit PCI slot and PCI X is the medium-length slot on the left