I've had both of them. The only real difference I can think of is that you have more spring options with the Hagons. If you're on the porky side, maybe 210 lbs or better, or if you like a stiff ride, the Hagons are a better bet. I don't have the Progressives to compare with the Hagons I currently have but I believe the Progressives had better fit and finish (setting the preload seemed smoother or easier). Again, I'm fuzzy on it, but I think the Progressives also had one more preload setting. You can get a standard or a heavy duty spring with the Progressive 412s. I weigh 210 lb and found the heavy duty just fine. I'm always been happy with Progressive's stuff and wouldn't hesitate to recommend it.
Price is about the same.
Overall, I would go with the Hagons, mainly because the people who sell them:
www.davequinn.com know what they're talking about and can tell you what spring is going to be right for you and if it isn't, will let you swap it, no springs attached (wasn't that punny?).
