....The WS is nice on account of the higher grade components (completely overkill, but still neat) and the PLX chip meaning all 16x PCIe all the time for all the slots .
WS has 7 PCI-e 3.0 x16 slots but when all are in use (with 40-lane processor) only one of them is operating in x16 mode, others are x8. Which is still more than enough for practical applications. WS is ideal for high-end workstation packed with cards, it accepts up to 128 GB of RAM:
http://www.asus.com/Commercial_Servers_Workstations/X99E_WS/specifications/