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

2 SSD module is connected to a host either through a SATA interface or via a PCI Express lane Though supports both SATA and PCIe, an

2 SSD will support either SATA or PCIe, but not both at the same time In addition, system board sockets will be designated by manufacturers to support either

m2 slot screw QNINE Dual PCIe Adapter, M2 SSD NVME Or SATA 22110 2280 2260 2242 2230 to PCI-e x 4 Host Controller Expansion Card with Low Profile

m2 sata slot Size: has three specifications: 2242, 2260, 2280, they just represent different sizes of SSD 2242 means 22 x 42 ,