DOT4 absorbs moisture. DOT5 does not. The difference other than that is the boiling point and DOT5 will not attack paint, as previously mentioned.
I like DOT3. It's cheap, always in stock and the amount of moisture it absorbs is minimal having to do with operation. Since DOT5 does not absorb moisture, it collects in various places through the system and sits there. To me, a fluid that absorbs moisture is what I want. Besides, I drive my car on the street and don't drive it like a race car, so the temperatures in the brake system are relatively low. Vehicles have used DOT3 for almost 100 years and it works well.
Lastly, be advised, In order to change from DOT3 or DOT4 to DOT5, you are supposed to change the entire system. In other words, all new brake parts. You cannot mix DOT5 with DOT4 or DOT3. At all. A lot of people think you can just flush and go. A complete system changeover is the only correct way.