I actually have the Alpinestars Paragon pads, both the arm and leg versions.

I don't have a whole lot to compare them to. They're moderately bulky, so a bit worse to pedal than a lightweight G-form pad. They're still not bad, and I don't have any trouble doing extended climbs with them. The pads have double silicon strips top and bottom so they stay in place reasonably well. Elbow pads are easy. The grippers on the knee pads hit right where my quad tapers in at the the knee so the top tends to slip a little. I've got pretty big quads (think sprinter) so if you've got less well defined quads it won't be much of a issue.

Ventalition wise they feel pretty good. The pads actually have a lot of holes in front so they vent decently well. Still they're pretty bulky and I tend to reserve them for more technical riding or colder days. Summer riding on my regular trail, I'll just go without, since I tend to do non-technical riding.