I've built and tested bows with all of them, Hickory, elm , maple and yew all faster than boo . Boo feels a bit smoother to me but if I were building a bow I had to depend on for my life it would be good clear edge grain maple. Next would be hickory but maple is more homogenous. Elm has a very coarse interlocking grain. I like it real well but it is a bear to fill and seal the edges of elm on the limbs. I have also had a harder time getting good edge grain elm and hickory compared to maple.
I am not a fan of walnut. Some of it seems to have a property that does not adhere to the glue well. I have seen several walnut lam bows delaminate in my lifetime and it was always the glue line. But there are thousands of bows build that are over fifty years old with maple lams that still are going strong and some of them have hundreds of thousands of shots under their belts.
I believe that Howatt, Pearson , Wing, Bear and all those great bow companies knew what they were doing and its a proven thing.
If you want flatout pretty though. Yew cores look fantastic and so does tigerwood, perhaps the unsung great core wood.
God bless, Steve