Different DOT ratings have different dry/wet boil points.
DOT4 has a higher boiling temperature.
Some racing fluids have bigher boil points, but keep in mind that the higher dry boiling points that the brake fluid has, the easier that it absorbs water. Iwouldnt change types.
Dot 5 is silicone based, and does not absorb water... but not compatable to DOT3, or DOT4.
DOT 5 fluids need different care.