If you're serious about boosting and making serious power, the only way to go is with the BP. On a stock engine, you're good for 350whp all day long(20-25psi). Build the bottom end, and you're good for 500-600whp. If you want to rev too, it's good for 7800 on the stock valvetrain, 9000 with upgrade valvetrain.
There are a couple of 2.3 drag cars making upwards of 1000hp, but that's the crazy s*** you see in magazines, with almost nothing stock. The advantage right now is for the BP, because of available aftermarket support(thank you Miata guys), but in a few years, I'm predicting the support for the 2.3 will be awesome, since it's in both the 3 and 6, and the Mazdaspeed6 is going to have a 280hp turbo version of the 2.3.