12:30 a.m. on April 18, 2013 (EDT)
The problem with a parka cut, in my experience, is that while it works fine for walking, it limits motion for climbing, scrambling, or any other activity where you have to be able to move your legs and back fully. Depending on how you hike, though, that may not be a problem.
The other difficulty is that the design doesn't really work well for carrying a modern, form-fitted backpack vs an old exterior rack. The pockets are in the wrong places for easy access, and what might be a nice down pile without a pack can get squished down quite badly with any weight compressing it it. Not a big deal if you're riding a snowmobile or pushing a dog sled, but it could be a problem if you're on foot.
Rob specified that his definitions were general ones, and I fully agree that for practical purposes, you can rate a shell as hard or soft simply by how it feels and buy target performance. Getting the perfect combination of weight, waterproofness and breathability, has been the holy grail of the outdoor garment industry for decades, and sometimes the line is blurry when you get into hi-tech comparisons.
Generally, a shell meant to protect against wind and be waterproof in the worst conditions will have a hard, non-porous surface that water beads up on and runs off. The water that does soak in, doesn't penetrate to the inside. DWR (Durable Water Resistant) fabrics are normally a nylon shell with a sprayed-on coating that makes water bead up and roll off, but whatever does penetrate the coating, along seams or driven through by the force of a storm, soaks through and you get wet.
A shell meant more for insulation, where some water resistance (rather than absolute water proofness) is needed, will usually have a more porous surface. In modern softshells, looks for the ones designed on the old Eddie Bauer model, where a loose, soft inner layer was combined with a tighter, exterior weave for extra wind protection. Not perfect, but it can be coated with DWR for use in light snow or a light shower.
Variations are available, and many fabrics have been tried out. At present a hardshell will usually incorporate a fabric like Gore-Tex, which relies on the difference in molecule size between water droplets and water vapour molecules to let wet air pass through and keep rain water out. I believe eVent uses the same principle, as do Pertex, Omnishield and a lot of the others.
I love my old Sorel jacket, made with Omnishield, quite breathable but more water resistant than waterproof.
I've tried Pertex, the standard for British military and SAR. As a stand-alone shell, I wasn't happy with how it worked in a driving thunderstorm. I could feel the water gradually soaking through.
Interestingly, the Buffalo shirt that is the preferred military garment has a Pertex (hardshell) shell bonded to a fleece (softshell) inner layer. The assumption seems to be that even if you get soaked by sweat or rain, you'll stay warm anyway. I actually discovered the same principle on the Jacques Lake trail a few years ago. When my Sorel got soaked through, the fleece I was wearing underneath, even though wet, kept me nice and warm. Reduced evaporation = reduced heat loss, I guess.
I've tried Polartec and while I think it qualifies as water-resistant, like the DWR materials, I would never trust it in either a heavy thunderstorm or steady misting soaker. The surface is too porous and seems to hold water that would eventually soak through. But maybe I'm just not giving it a fair test - if I'm expecting rain, I'll always cover it with a waterproof hardshell.
For hiking on the BC side of the Rockies, I'll wear my OR Gore-tex Paclite Shell. While not as breathable as Gore-Tex ProShell or the rival Neoshell, it's very light and completely waterproof. See my review.
You might want to note that in my experience the manufacturer is less important than the fabric the jacket is made of. Pattagucci, Dead Bird, REI and MEC, and TNF all sell Gore-Tex jackets, and they all buy the fabric from the same factory. It's the fabric that makes the difference, more than variations in design. I have to admit that I get pro-deals on a lot of my gear, though, so cost is less of an issue and I can buy big-name gear when I want.