This is just a guess, having read a fair amount of tradgang posts over the years (even if I haven't posted very much myself), but I'd say you're going to get a lot of opinions here with about 50/50 yew/'boo (mass or otherwise), with many saying both woods make a great core, and it will ultimately be suggested to you that it's a personal decision, and that you should try each, preferably side by side, and see which one you like more. People may also suggest that the answer would differ depending on the type of longbow you're talking about (ELB, AFB, Hill, RD, glassed or not, etc.)
Assuming you haven't already, you might also want to check around the forum for topics addressing the same sort of question/s you're asking here. You might also find some other valuable information, such as comparisons to other types of core woods that might be of interest to you (assuming you haven't already considered and dismissed these other options), etc.
Good luck with the research and the new bow. I happen to think 64" is a great length for an RD longbow (which is what I'd guess you were talking about because of the bow and draw lengths). Tradgang is a fantastic resource and you should find some excellent and intriguing information here to help you make your decision.
Oh, I suppose I might as well give my opinion here: Having shot several 'boo bows (action and cane), I'd say they're solid. I can't compare them to yew bows, however, as I don't think I've ever shot yew. I think the idea of a yew longbow is pretty nice, though - yew often being considered the quintessential longbow wood. If I was to buy a new longbow right now, all else being equal, I'd probably go yew because of it's history and reputation and largely because I already have 'boo bows and yew seems like it'd be fun to try.
All this being said, they're both great, it's a personal decision, I'd recommend you try them both, preferably side-by-side, and decide for yourself
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Once again, good luck!