Natural reflex is MUCH better, and natural reflex is much more likely to remain after the bow is finished as opposed to induced reflex. Here's my take on why that is:
When wood is freshly cut, the cells are saturated with their own natural moisture and the wood is almost malleable, like soft metal. But as the wood dries, the wood cells will become "locked" into whatever shape they are held in. Regardless of what shape you bend that stave into, the wood cells will always "remember" the shape they originally dried in and will always want to return to that shape. That's why you can reflex a stave into a circle, but as soon as you string it, then that reflex is lost. But if a stave dries into a natural reflex on its own, then those wood cells will always return to that shape because that's the shape the wood cells "remember". Try straightening your arrows while they are still green, and you'll notice they stay much straighter and will warp less once they dry.
I honestly believe that is why the northern California bows are so heavily reflexed, even though they are so short. Those guys hacked their bows out of green yew, then carefully seasoned it (at least partially) and then sinew backed it. The sinew helped, of course, but it was the drying of the green wood into a natural reflex that made the difference.
Several years ago I visited the Museum of the American Indian in Washington, D.C. and I saw some Nootka halibut hooks that blew me away. They main body of the hooks was made of pacific yew, but they were bent into a horse-shoe shape, with elegantly curved ends. There's no way in hell you could do that with dry wood...the wood had to be green (and was probably heated as well), then it was bent into that shape and left to slowly dry. That's how those guys were able to manipulate wood into seemingly impossible shapes. I included a picture of the hook below. Try doing THAT with dry wood!
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