We owe a lot to the Gore people for creating the first w/b membrane that has made it possible for us to be slightly more comfortable and safe in the backcountry. As with all technologies however, especially as long as Gore has been on the market, there is bound to be another company come along that figures out how to do it better.
First, the story about Gore-tex (short and sweet version). Gore-tex started out with their First Generation which was the most breathable of all the current Gore-tex membranes. However, it wasn't able to combat oils, dirt, and other contaminates which would cause it to leak (yes, Gore-tex can leak). The reason why it is possible for it to leak is that most of the membrane is space, 80% to be exact. It is true that by taking a square inch of Gore membrane you get 9 billion pores that are smaller than a water droplet, but larger than a water vapor. However, the size of the pores aren't what keep the water out or results in a material that's durably waterproof (waterproof that can withstand pressure). This is accomplished by it's surface energy. Without this surface energy (weak bonds of the water molecules), water would find a way to seep through the pores no matter how small and no matter what state they were in. Again oils, dirt, and other contaminates broke down this surface energy.
Gore-tex then upgraded the membrane to the second-generation. This was the same as the first (ePTFE or expanded Teflon), but with an added layer, PU (polyurethane). This PU layer combated the contamination breakdown allowing the membrane to maintain it's surface energy no matter how dirty the membrane got. Thus it solved the "leak" problem. However, it created another. PU is a hydrophilic (water-loving), monolithic (solid) membrane. In order for the water to pass, it has to 'diffuse' (going from a lesser concentration to a greater) through the solid PU membrane which can easily become overwhelmed. At this time, Gore-tex still remained the most 'breathable' when compared to other membranes and coatings because the PU membrane was so thin. Gore was able to attach a very thin PU membrane to the ultra-smooth ePTFE membrane unlike other PU membranes like Marmot's Precip or The Mountain Hardware's Conduit which had to be much thicker due to the lumpiness of the nylon or polyester in which it covered and had to adhere to. So even though PU was the culprit for creating less breathability for the 2nd gen Gore, it was still more breathable than any other PU membrane available (at that time there was only one ePTFE/PU membrane, Gore-tex; all the others were PU). Second Generation Gore-tex includes Goretex Classic, XCR, Paclite, Windstopper, and the new ProShell (these all include a thin PU membrane). It's true that XCR and Paclite is slightly more breathable than Classic, but not by much. ProShell is identical to XCR except for the tricot protective 3rd layer. Instead of using tricot, ProShell uses a durable protein layer that protects the vulnerable Gore-tex membrane from abrasion but allows it to be lighter and more packable. Packlite, again identical to XCR, does this as well, but isn't as durable as ProShell. It's all pretty confusing. The thing to remember is that XCR, Paclite, Windstopper, and ProShell all have the same breathability.
eVent (created by BHA Technologies
in Kansas City, MO, a division of GE Corp), on the other hand, is the only other ePTFE available and the only one that doesn't use PU. What makes it unique is that it uses a patented super-critical gas treatment to encapsulate the ePTFE membrane with a polymer that is hydropholic (water-hating) and oleophobic (oil-hating). This polymer does the same thing that the PU membrane does for Gore-tex (that is maintain the surface energy), except for the fact that it doesn't inhibit it's breathability. Thus eVent is 30% (high humidity levels) to 200% (low humidity levels) more breathable than Gore-tex! This goes beyond it being significant; it is a staggering difference. One other thing to keep in mind with Gore-tex when comparing it to eVent is that Gore-tex works best at high humidity levels. What this means is that in order for Gore-tex to work optimally, there needs to be 100% humidity inside the jacket. This obviously is not good because that means you're, at the very least, clammy (we've all experienced this with a Gore hardshell) and at the worst, wet! Remember the PU is hydrophilic (water-loving). The PU absorbs the humidity and transfers it to the outside. Gore-tex believes this is good because it works best when you sweat (it really isn't that good). However at low-humidity levels, Gore-tex is almost worthless because it can't transfer moisture due to the solid PU membrane. eVent, on the other hand, works best at low-humidity levels (when you need it most) because it allows the early water vapor to escape, not allowing the jacket to get to the high-humidity levels that Gore works 'well' in. Thus you don't fell clammy. It's interesting to note that even though Gore's best results are at high humidity, eVent still out-performs it by 30% at these levels (this is according to non-biased Army lab tests)!
As you can probably guess, I'm not the biggest fan of Gore, although I own several pieces. Gore did a great job in selling me into it. Now that eVent is available, and since I've been using it, I've noticed a HUGE difference beyond lab results and marketing. The stuff is incredible and has given me the desire to wear my hard shells again. eVent is really the future of w/b material and if you are planning on spending your hard-earned cash on a $400+ shell, you would be nuts to buy Gore. I learned this through several training sessions and my own research after picking up the new outerwear line Westcomb
(the best eVent stuff available) who uses eVent exclusively. It has been an eye-opener to say the least.
Gore-tex is still the king of the hill and has a huge marketing budget. Because of this, and other financial reasons, you most likely won't see companies like Mountain Hardware, Arc Teryx, Patagonia, Marmot, The North Face, etc. using eVent. In fact, Gore-tex has told these guys that they will no longer be allowed to use their membrane if they use any eVent. Nike, who doesn't need the marketing dollars, has dropped Gore completely. You might see others following suit once the word gets out. As of today, Westcomb is the only high-end manufacturer, made in North American company who uses eVent. We are also the only direct competitor to Arc Teryx based on quality and similar specs. It is really nice stuff and the fit is amazing!