I've used both on Yew with success, to me the advantage of steam is you won't overheat the wood, but you've gotta be damn quick clamping it to a form.
The advantage of dry heat is you can shape and temper at the same time.
Use which ever is easiest, most convenient and the method you feel happiest with.
My big mistake is always working the bow too soon after heat treatment... leave it 3 days to be really safe, certaily no less than two, unless you like doing the work all over again!
If the stave has been roughed out and you use dry heat, protect the sap wood with a couple of layers of masking tape and duct tape, don't want to risk scorching that lovely creamy sap wood.
Del
