p28 doesnt support a knock sensor
either one is a good choice
p30's might be hard to find (never looked for one but the Del Sol with the B16 is kinda hard to find so id think the ECU wouldnt be the easiest thing to get either)
as for what will be faster... couldnt tell ya
i would go with the p28 just because of the possiblities with programs and aftermarket with that ECU but in stock form the p30 is better but more pricier and (to me) a waste of moeny...if your going to chip the ecu stick with the p28 there are more options but if u want to keep the ecu in stock form get the p30 but have fun finding it for a decent price.....