If you use song mode then you need to be using MTC. MTC will tell the MPC exactly where in time the sequence is. Make sure the tempo in DP and the MPC are set the same. MTC is not necesarily tempo dependent.
I don't know if one is "better" than the other. Generaly if you are working with any type of video sync you will use smpte. MTC is almost always used to sync midi unless you are locking to analog tape.