That is interesting. Do you mean 40% of all your CPU cores? And was that with oversampling switched on or off? The IK stuff seems to use a lot of CPU when it's in high quality mode.
I prefer A, I like the extra punch in the low end. It sounds like it's overdriving slightly which I like. And there's a bit more air around the sounds. I would guess that B is IK as my experience is that it sounds a bit 'safer' than the UAD stuff. And if B is IK, it sounds like you *might* have oversampling switched off, because the high end air drops a bit. But I wont be gambling my house on any of that...!