I'd go with white oak for your first bokken. If you want to start collecting the things you can experiment with more exotic woods later.
Isu is at least some places only recommended for light contact. So it gives you less options. Of course it depends on the kind of practice you expect to do. In our dojo we sometimes bang bokken/jo against each other with some force and I'm very happy with how my standard white oak bokken holds up. I've seen a couple red oak jo split in half. Though a jo is of course a bit thinner.
Something like this is what I mean:
I haven't actually bought a bokken from Budogu but clothing and some gifts, and they've always been very helpful.
Kingfisher I have no experience with but from what I've read here people seem very happy with them, too. Did you read the page on choosing a bokken on their website?