I've got two dry staves of red oak, locally grown here in the Netherlands. I've removed the sapwood from one, just because the heartwood seems a bit denser. Not sure if that is the case, but I like the color of the heartwood over the sapwood. I have yet to start a bow from this wood, though. A friend of mine made a nice flatbow from the other half of the log. I rate red oak higher than European oak. But European ash might be a bit better still. But not necessarily, as European ash is very variable.
I remember Tim Baker stating something like: "if the boards weren't so darn cheap, every bowyer would be thrilled with a red oak stave."