Well some say its better and some say its worse.
As far as i'm concerned..
Burnout Revenge improved on a lot of things I didn't like in Burnout 3. But they were only small things. The motion blur was reduced a lot, the cars had a little more weight to them, the tracks were more interesting designs, it had more interesting sound effects and so on. Thats the end of the good. There were a lot more things I didn't like from Burnout 3 that werent improved however.
Traffic checking while on one hand was quite fun, made the game far far easier than it should have been. Takedowns are quite fun, but make the races far easier than they should be. Seeing a pattern? The crash mode is the worst the series has. It was suffering very badly from more-of-the-same-ism.
Paradise on the other hand is.. Well, very different. I think it's the best game in the series since Burnout 2. But ironically enough, I think the races are the weakest part of the game.
Well I don't have time to list every detail about Paradise vs Revenge. However, given the choice it's Paradise over Revenge any day.