It depends in what way, looks or sound?
Since pedal harps are mostly made from maple and veneered with other woods the final veneer doesn’t have that much of an effect on the sound and is primarily cosmetic. In that case I like Cherry and Ebony.
For lever harps where the many of them are made from the solid wood which has a greater effect on the sound I like Cherry and Black Walnut, but most of all I like Koa. Unfortunately Koa wood is hard to get these days so I don’t think too many harp makers are producing lever harps out of Koa anymore.