The differences are glycol based versus silicone, boiling points, compressibility, and if they are hydroscopic ( absorb water ) I have always thought that Dot 5 was originally invented towards things like the military where they knew moisture was an issue. Then there is performance, and some say that Dot 3 and 4 are better performing due to resisting heat better. I have seen one bike that the rear brake line was routed too close to the exhaust and the fluid failed ( my neighbors wife's bike when we were riding ) Changed the fluid and moved the line slightly and no problem. However, like Wristpin said, I have not seen any corrosion or hose destruction. That's the good part of Dot 5, and your paint.