Toda only makes one set of Spec B cams and it does not have stock primary/secondary lobes so that comparison is a bit moot.

In general a cam profile is only good to a particular RPM. Generally you put the VTEC crossover at the point where the power curves intersect for each profile (primary/secondary and mid). If you have stock primary/secondary lobes and a bigger-than-stock mid lobe, you move the point in the RPM band where the mid lobe profile becomes effective but do not extend the range what you get is a flat spot. If you leave the VTEC crossover where it is, you get off the primary/secondary profile before they can run out of juice but you're out of the optimal range for the mid profile. If you move the VTEC crossover up to where the mid profile starts breathing then you stay on the primary/secondary lobes for too long. Either way is less than ideal.

I can't think of a decent performance-oriented reason to retain the stock primary and secondary lobes. Their main purpose is to keep the motor from falling on its face before you hit VTEC while at the same time keeping fuel consumption to a minimum. If you want to see the most worthwhile increase in power you have to go with a cam that is designed to greate power both before and after the cam switchover.