M.2 vs. U.2

Solution
Both 32 gbps max theoretical speed, on PCIe 3.0 x4 lane. The M.2 is dedicated to only M.2 connections, whereas the U.2 can be setup as Bluetooth, wifi, ssd or obviously U.2.
Best advantage goes to M.2 at this time, as the M.2 interface storage available has the greatest variety and lowest cost vs U.2.
Both 32 gbps max theoretical speed, on PCIe 3.0 x4 lane. The M.2 is dedicated to only M.2 connections, whereas the U.2 can be setup as Bluetooth, wifi, ssd or obviously U.2.
Best advantage goes to M.2 at this time, as the M.2 interface storage available has the greatest variety and lowest cost vs U.2.
 
Solution
M.2 and U.2 are the same. They both use PCIE 3.0 4X connection and both have the same protocols. Basically, its just preference if you want a external drive or one stuck on the motherboard. So far only 1 company makes consumer U.2 cards which is Intels 750. It didn't take off like SATA, but i suspect onces people want more than one M.2 drive per computer, people will start buying these up.