I didn't own the F9 Pro before but had a F9 once and now using the B400. I would think that the F9 pro with the dynamic driver would have a more thumping bass than the B400, but this does not mean that the bass of B400 is anywhere lacking, but its perhaps more precise as it uses a BA. I don't listen to melodic rock, more of slow rock and pop. I do find the B400 sound lusher with all the 4 BA firing at the same time compared to the F9, producing more texture and a fuller sound, hence I find it more value for money. however, due to individual preferences, you should read the professional reviews and comparisons, as well as try both out before deciding.