A nova and Jp are going to be close, I have ran the P-5 but not the b-5.
A few guys I race with often run the Plus 21 and their cars are really fast and look to be good engines.
If I was goin to choose between 2 motors it would be a Werks Team Line B-7 and the Ninja. I ran a B-7 for almost a year and it proved to be one of the best motors out there.