From what I know, Multiband EQ is a more recent (so maybe better optimized?) addition to FMOD than 3-EQ. And HighPass and LowPass are legacy (for retro-compatibility), so maybe better to avoid them…
I just did a little test with 20 effects of each on a single event, and Multiband EQ seems cheaper on the CPU. Here’s the result:
But maybe with different settings, the result would change, I don’t know…
Nobody can answer but you. Just try! (but I would tend to say it’s often possible)