Now does lets say a set of JD long travel arms make the bike handle differently than a different brand of long travel arms like Roll Design or Walsh of the same width? Or is most of it in the durability?
Handling is a subjective opinion. What could handle perfectly for one person could suck for another. Some people like the twitchy, light feeling of a ProTrax front-end. Some like the solid, planted feel of the Roll. I myself would go for the Roll.
Personally, I'm not a huge fan of the kingpin setup on the Roll front ends. I like the sealed FRAP ball joints like on my JD arms. If I remember correctly, the kingpins from Roll are like $50/piece x 4. That on top of the spherical bearings for the lower arms and the heim joints on the top makes for one really expensive rebuild. Which setup lasts longer? I can't say. The Roll stuff is used by a ton of desert racers and is virtually indestructible, so it's proven. The Roll arms arms are beefy as hell.
I was initially concerned about the toughness of the JD arms I purchased. After all, they were almost half the price of new Roll arms. But I was seriously impressed when I got them. They're some really solid units