......................... I've always went with 40(20 a side) on my sebenzas, and most all other knives. You would have to remove steel getting it down to 30, and it will take a while. Hit them on 40 and they'll be popping hairs again in no time.
40 will give you a tougher edge, but its still plenty thin enough to make for a great slicer as well. Best all around edge angle IMO.