I wear Darien pants on the bike. I used to wear First Gear HT2 pants.
They both have full-length side zippers, but the HT2 have full-length velcro that makes the zipper a royal pain to use. They are simply more time-consuming to get on and off which is fine once in a while, but gets old fast, especially on those days when riding is comfortable but you want to shed a layer fast in a hot parking lot. The HT2 are not available with long inseam for waists under 34". These have multiple layers of lighter fabric which flap a lot in the wind.
The Darien zippers have inside and outside flaps, but less than a foot of velcro at the hip so they go on and off easier. The flaps don't LOOK weather-secure, but they work perfectly. The Dariens are available in many sizes and can be modified right there in Duluth. The regular Dariens have a single laminated layer which doesn't flap so much in the wind. The armor in the Dariens is far better than the foam padding in the HT2s.
Both pants keep the water out and keep some warmth in.
For me, the shape of the Darien waist fits far better -- the pants just stay there. I was always pulling up the HT2. Mine are both 32" waist.
"The belief that there is only one truth, and that oneself is in possession of it, is the root of all evil in the world."-- Max Born, Nobel Physicist