Not to sound impolite but we do have a
Shin Megami Tensei thread over here.
But since it's already here, to your question. I personally think P4 has this same issue you pointed but if memory serves me right I think there are more character interaction, even if not story based, oh and there are a lot more events too, so even if there are moments the story goes at a slow pace, there are more stuff to keep you busy.
Another thing, I think the characters in P4 more more lively and fun so that makes each moment with then more enjoyable.