No, I haven't been on it, and it would not surprise me if I came off Mission Breakout thinking it's more "fun," but it's really an apples-to-oranges comparison. The two attractions are trying to evoke different responses and create totally different moods. One is trying to be just a blast of excitement, while the other is going for something much more eerie and creepy.
For its placement in the park, I think Tower of Terror is absolutely brilliant, and one of Imagineering's crowning achievements in placemaking.