I won't attempt to add any more data to the other two answers posted here, but in my own experience eVent really does seem to be more breathable, particularly at warmer temps or in more humid conditions. As the outside temperature drops and the temperature gradient across the jacket membrane increases then in my experience Gore-Tex 'catches up' performance-wise. An interesting side-effect of eVent's breathability is that it doesn't seem to retain heat as well as Gore-Tex. That's a personal opinion, but in my experience it seems to be true - I feel like it is necessary to wear a heavier layer underneath to compensate in colder weather. Another waterproof/breathable material that shows a lot of promise is Schoeller's c_change. I haven't gotten to use this in the winter yet, but for summer hiking/backpacking the Cloudveil Koven Plus jacket performed admirably, especially considering that it is designed as a winter sports jacket. Anyway, long story made short: for warm/humid conditions eVent seems to be superior. For cold-weather activities I prefer Gore-Tex. Pending further usage I'd be willing to consider that c_change might just be the best compromise of the two for all-season usage. Of course, that's all just my opinion.

There is an incredible amount of marketing spin when it comes to w/b laminates. Gore-Tex would have you believe that it has the superior product as would eVent for obvious reasons. Based on the price of the garments offered from various manufacturers, if you're paying $400+ you had better be sure that you're getting the best, most capable piece made! Their entire reputation is dependent on how breathable their respective laminate is... I would disagree, in part, to what the head of the Arc'teryx Soft Good Design guy has said. He has totally bought into Gore-Tex spin. The fact is the Sweating Hot Plate Test that Gore uses makes them look better. It's essentially a test done by using a porous metal plate that's heated allowing steam to work on the inside of the suspended material. This, in essence, shows how much water vapor can pass through the membrane at any given humidity level. As the steam passes through, it's resistance is recorded which gives it it's RET reading (the less resistance, the more breathable). The RET is a scale that lumps all w/b laminates into a series of categories starting with extremely breathable, then very breathable, then somewhat breathable, and so on. Gore-Tex ProShell and eVent fall into the Extremely Breathable Category, but doesn't give much detail other than that. A better test is the DMPC (Dynamic Moisture Permeation Cell) Test developed by Dr. Gibson of the US Army. It essentially tests not only the inside humidity (Sweating Hot Plate Test only tests humidity INSIDE the jacket), but the outside humidity as well. It should be noted that there are ton of other variables, such as the face material and the person's metabolism, that can also effect the laminates breathability. Because of all these variables, the best test is the actual usage of the materials in real world conditions. One erroneous comment made by Arc'teryx's Soft Good Designer is that eVent becomes contaminated over time with oils, This is simply false! They use an encapsulation technology that essentially coats all of the ePTFE nanofibers with an oleophobic (oil-hating) polymer. Gore-tex does this by using a hydrophilic (water loving), monolithic (solid) polyurethane membrane. The key here is that it's SOLID, meaning the water has to diffuse through the membrane. eVent on the other hand works because it is completely porous. There is no solid membrane holding back the vapor. This is the great secret! Therefore eVent will ALWAYS be more breathable than Gore-Tex until they can do away with the PU membrane! By the way, on the RET scale, eVent is 3-5 vs. Gore-Tex ProShell at 4-6. What Dr. Gibson's findings showed eVent works from 30% (high humidity inside the jacket) to 200% (low or no humidity inside the jacket) better than Gore-Tex. The bottom line is you will feel clammy in a Gore-Tex shell and not so in an eVent one. Event is simply more breathable! Companies can use any form of marketing they want, but in the end, the fact remains that eVent is the king of breathability, period. Durability is a question and eVent hasn't been on the market long enough to show any superiority here. Gore-tex has been around for 30 years and has been shown to be very durable in extreme conditions. The question resides with the manufacturer. Westcomb uses a process which forces the glue through the membrane onto the face material when taping the jacket. It is incredibly durable and has seen very few delamination problems. Gore-tex's argument that over the course of time eVent clogs is simply false. There is simply no evidence of this. I put it to Gore-tex or Arc'teryx to show some real world data that would show this is the case. I call it marketing spin! The two best manufacturers of outerwear currently are Arc'teryx (Gore-Tex) and Westcomb (eVent). You will see similar construction (i.e. 16th of an inch seem tolerance, narrow seam tape, 20-25 stitches per inch) and fit (both are the top of the pyramid in this aspect). If breathability is really important, and it should be, I would go with Westcomb! However, Arc'teryx has a huge selection of incredible jackets and outerwear that are all immaculately made. Where I agree with the Arc'Teryx Soft Goods Guy is in his comment that an 'important consideration in buying a jacket is Design, Construction, and Materials'. Other than using Gore-tex in materials, Arc'teryx has few rivals...Westcomb really being the only one (in my opinion). There is a tremendous amount of information on the web concerning Gore-Tex and eVent. REI's Expert Advice under "Rainwear: How It Works" is one of the best I've found. They, of course, sell both Gore-Tex shells and eVent so you should expect a fair treatment of both products. They have also come to the conclusion that eVent is far more breathable. Get the Facts!!!

Here's the company line from the Arc'teryx Head of Softgoods Design: "This is a highly debated area with more spin than a your average roller derby. We have generally tried to stay clear of these numbers because our cumulative years in the field has taught us that true performance/comfort in waterproof breathable fabrics comes from a synergy of many different elements: · Face fabric. · DWR. · Membrane/Evaporative resistance. · Resistance to oil and other contaminants. · Internal moisture dispersion/ backer. · Garment design, fit and construction. ……and the longevity of each of these elements. For those driven by figures: all our Gore-tex fabrics have a Hydrostatic head of at least 28 000mm which equates to 40PSI. Gore prefers to use as RET values as they, like many, believe that it gives a better correlation to human comfort than Mvtr. Our Values here are all lower than 6 but I do not have a specific number for each fabric. RET values are affected by the weight and density of face and backer fabrics. The Pro-shell range of fabrics spans RET values from 4 to 6. (lower is better) I believe eVent claims an RET of 4.5, but this figure must change with each individual fabric combination. Best figures that I’ve been able to dig up is Gore 28 000 Hydrostatic head 17 000 MVTR again the inverted cup method used to measure MVTR has very little correlation to human comfort." With that being said, I've seen a few tests comparing eVent to Gore Pro-shell. Initially the eVent does breathe better, but since it lacks the oleophobic (oil hating) membrane of Gore-Tex, the eVent membrane tends go get clogged quickly, which in a short time, greatly reduces it breathability. Arc'teryx has tested every WP/B membrane out there, and still uses only Gore Tex Pro-shell and Paclite, because it maintains the highest level of performance for the longest amount of time. The more important consideration in buying a jacket is Design, Construction, Materials. Both Gore and eVent make great products, it's what the manufacturers do with those membranes that count. whew, that's a mouthful