I've handled both a fair bit. Choosing between them really comes down to:
1. Weight - The BO action is considerably heavier than the Defiance. Not sure exactly now much, but you notice it in your hand. The BO is not top choice for a lightweight build. However, the heavier action weight of the BO allows for a heavier contour barrel while maintaining the all-important BALANCE.
2. Bolt lift and throw (60º vs 90º) - While the M2013 bolt lift is improved over the M2008, it is still much heavier than the Defiance. You've really got to experience it "in action" to determine if it's a problem though. I don't mind the BO boltlift at all, my partner can't stand it. He does acknowledge though, the increased bolthandle/scope clearance provided by the BO is nice, and he loves how it almost seems to return to battery all by itself. Still, he just doesn't dig the increased force required to cock the action. It is what it is and this is a key point on your decision.
3. Stock options - Not a big issue, as all the big stock/chassis makers will inlet for the BO, or modify the chassis to fit the BO. However, you can just about forget finding a second hand stock for the BO, while you see them all day everyday here on the hide for the 700 clones like the Defiance.
4. Barrel interchangeability - probably hardly worth mentioning, but I will anyway. Barrels interchange from one BO action to the next, which is great for a switch barrel setup. However, I suspect the Deviant would allow for this too, even though they don't really make the claim.