These days, pretty much everything sold as waterproof is waterproof (except for Paramo, see below). Where jackets differ is in breathability, water repellency, and design.
Poor design will see rain getting in through the front zip, pockets, vents, neck etc. A good company will do a lot of testing of assorted designs in actual real conditions before releasing a product, whilst a poor company will just come out with something that looks right.
Water repellency is what makes water on the surface of a jacket bead up into droplets that roll off, rather than just forming a layer of water over the surface of the jacket (at which point breathability stops). It works best when clean and new, and different brands will have different tolerances for wear and contamination.
Fabric breathability is what prevents sweat and condensation from building up on the inside of the jacket and getting your inner layer wet. It's not magic, and will only allow water vapour out at a fairly moderate rate compared with the rate at which hard riding will generate sweat. It is after all perfectly possible to saturate a cotton T-shirt with nothing over the top, and you can't get more breathable than nothing.
The most breathable current fabrics are eVent, Goretex Active Shell, and Polartec Neoshell. These are breathable enough to use as a windshell on a cold day without getting wet, provided you don't work
too hard. There's a decent round up of assorted fabrics on the
Ellis Brigham website. An advantage (at a cost) of Goretex is that manufacturers must submit their designs for approval before being allowed to use the Gore name. This filters out the bad designs. EVent is available to manufacturers in an unbranded form, so some of the best "own brand" fabrics may actually be eVent. I suspect Endura;s "PTFE" as
Paramo:
This is not actually waterproof, as you will find out if you sit in a puddle whilst wearing a pair of Paramo trousers. However, it is generally pretty much rainproof , pretty much condensation proof, and is considerably more breathable than anything else. On the downside, it has a significant amount of extra warmth. so it would be like putting an extra thermal base layer on at the same time as your regular waterproof.
It works by having a loose water repellent liner layer, maybe 1 mm thick, that moves liquid water away from your skin or inner layers to its outside, where it can't get you wet. This is covered by a simple pertex windproof layer whose main purpose is to prevent raindrops hitting the liner layer hard enough to just force their way through (as in puddle water).
Because of the way it works, it's long lasting in that any tears can just be sewed up without affecting waterproofing, and the water repellency on which it relies can be fairly easily restored using a wash-in repellent (Nikwax).
Problems with it are weight, packed bulk, warmth, and that on rare occasions the repellency can be swamped so the it becomes waterlogged and fairly useless. This is usually due to either no maintenance (no washing/reproofing for too long), or excessive maintenance (reproofing every wash, matting the fibres on the outside of the liner together with accumulated Nikwax).
I found the Montane Stormrider (eVent, no longer available) the best jacket I've used so far, until I wrote it off in a flooded pothole. I replaced it with a Sugoi RSX (Neoshell), and also considered the Gore Alp-X 2.0 (Goretex Active). Paramo is too warm for me until it gets pretty cold.
- be it price, warmth or lack of it, breathability, fit "technical features" pit zips, drop tail etc
