In reply to Gaz lord:
The basic membrane in both Gore-tex and Event is expanded PTFE. This is a gas permeable membrane.
When Gore originally introduced Gore-tex, they used this membrane on its own, and it breathed beautifully. Unfortunately, it was found that the pores in the membrane became blocked by body oil contaminants, which led to a breach of the membrane by a process of reverse osmosis.
Their solution was to apply a thin PU layer to the ePTFE membrane to stop oil getting to the ePTFE. They don't like to talk about it, but, if you compare the breathability tests of Gore-tex and PU coated fabrics, you will notice that they behave in a very similar manner. Gore-tex breathes better than a PU coating because the PU layer is thinner.
Some Gore-tex fabrics are still pure, gas-permeable membranes that don't have the PU coating; Gore-tex Exchange, for instance, which uses the increased breathability and gas permability for applications such as bivvy bags and tents.
Event uses a different method of protecting the ePTFE pores, by applying a protective layer at a microscopic level, coating the inner surfaces of the pores themselves. Thus, the Event membrane remains gas permeable, as demonstrated by their 'bubbler' units.
Unfortunately, Event have also found that their pores become blocked by oil contaminants. However, their solution is to use a detergent wash to remove this oil, then wash with soap to remove detergent residues that would otherwise compromise the DWR (detergents are much better at removing oils than soaps).