Depends on what you want to do with your rig.

The X99-E WS uses a bridge chip to offer additional lanes of PCI-E. However these additional lanes only "exist" between the PLX-Chip and the attached peripherals.
If peripherals have to communicate with the CPU, it still comes down to the PCI-E bandwidth available on your processor.

So performance wise you add another circuit to the neighborhood which means increased signal length, on the other hand this does not so much kick in when using SLI for example, as the data send to the cards is the same anyways. (But can be a limiting factor if you use many PCI-E peripherals of different origin at the same time, like sound cards, USB/SATA extender cards, PCI-E based storage devices etc.)

OC-wise the R5E is clearly the way to go - you can customize nearly every setting you can think of.

To give you a short conclusion:
If you are not that much experienced or interested in OCing and tweaking then the R5E is probably not your board, as it can easily frustrate novice users, but once fine tuned there is really not that much competition imao.
The X99-E WS is more like the easier to setup and care-less-about-configuration brother in the X99 line. (after all the WS stands for "workstation" if I am not mistaken?)

If you are just looking for a decent "plug in and run" gaming motherboard, you might also want to take a look at the TUF Sabertooth:
https://www.asus.com/Motherboards/SABERTOOTH_X99/

Hope this helps. 🙂

The R5E is basically the Mount Rushmore of X99 motherboards, if you want enthusiast gear then it's an excellent choice.

The X99-E WS really offers no advantages over the R5E unless you want to pack that x16/x16/x16/x16 capability with workstation cards to do some serious number crunching. It has the same 3-way/4-way/quad SLI limits as the R5E in terms of graphic/gaming performance, PLX might be able to split and multiply maximum lanes but at the cost of added signal latency - the R5E would always have equal or better SLI/CF performance, although perhaps by a very small margin. The extra lanes on the WS might offer a wider range of possible options for PCIe-form-factor storage devices, if you need tons and tons of ultra-fast parallel storage.

Both mobos have the same Asus OC Socket, so they'll have essentially the same DIGI VRM phases, electrical hardware, heatsinks, and EUFI/BIOS firmware to drive it. Both have the same audio, USB, LAN, etc. The R5E ships with a useful 3T3R WiFi accessory (and now also a USB3.1 card), the WS doesn't. The WS supports JEDEC ECC DDR4, if that's your thing, but the R5E doesn't. Both mobos support the same Core-i7 and Xeon-E5 processors. I expect (hope) that Asus would work hard to support "workstation" products, but I don't know if they do. The "flagship" R5E has aggressive support for extreme DDR4 and general gaming hardware, and I expect that it will continue to command the lion's share of Asus attention until they release a newer and better "flagship" product. You'll find a lot more setup, overclocking, and troubleshooting guides/info for the R5E than for the WS. And these mobos have different styles and colours. The R5E's ROG red angularity is cool enough, but I personally find it somewhat garish and gamey, I would much rather prefer an R5E with the slick glossy/matte black WS look.

But if you don't really plan to use 4-way multi-GPU support and enthusiast overclocking madness ... the basic Asus X99-A is also a fine mobo and (just like the WS) it also has the same Asus OC Socket plus the same pile of onboard hardware. Perhaps not quite as robust when pushed to the extremes, but also a whole lot less expensive.

If someone have more than 2 or maybe 3 cards I think X99 E WS is even better option.
Simply Rampage 5 EXtreme have that stupid USB 3.1 Port card and that could be problem if someone have i7-5820K and some nice sound card.
From other side X99 E WS have normal USB 3.1 connectors on back side and you don't need to install in x8 slot only for two USB 3.1 ports.
You see plan is 3 GPU and I would definitely go in that case with X99 E WS USB 3.1 because it's funny to someone buy that board for single card.
If they plan to work as server board probably is very good on longer period.

I'm not sure about video but I know the disk IO that I had by trying to use an OCZ Revo3x2 240GB in the slot on a Maximus VI PLX chipped lane PCIE slot using the 4770K sucked so bad I took the card out and used only 1 of the 2 I had until I upgraded to the RVE and 5820K. Now I use both and they rock 3GB/s in wintendo 10 stripe.

Somehow I think using PLX for video will suck.

well it's already been proven that 16x vs 8x doesnt make any diffrents in performance. RVE is aimed for hardcore overclockers and hardcore gamers, it's the ''most opened up board of them all ''Asus motherboards''. PCI-E Speed doesnt make any diffrence in performance aslong as it's (Gen3) the (Gen) is the performance diffrents.

from Gen 1 to Gen 3 is a big leap in performance but 4x , 8x and 16x speed in gen3 doesnt make a ''Huge diffrence'' so don't fall for the 4x sli in 16x busspeed or 16x16x8x or 16x8x8x. and to use 4 graphic cards in SLI is just plain stupid. from 1 card to 2xSLI gives the best boost, with a 3rd card you get another boost but not as much as with the second card ''Performance wise per card'' a 4th card wont give you a huge benefit or leap in performance and you wont be able to hit 100% from the 4th card, it's just a waste of money to be honest. just my advice 🙂


here is an example ----> https://www.youtube.com/watch?v=rctaLgK5stA

Both boards are nice...
Advantage of WS version is Internal USB 3.1.
Except that Rampage 5 Extreme is little nicer inside case when you build everything.
I would save 100$ and build everything on Rampage 5 Extreme, except 4way SLI.