You really have two questions here. Your title says "What's best..." That largely depends on the situation. Different traps function better in different situations. That's why I encourage folks to become proficient with the three major devices, foothold, snare, and bodygrip (If you're writing a paper, make sure you have your terminology correct. Conibear is the registered trademark of Oneida Victor, that type of trap is a bodygrip trap.)
So, there is no definitive answer as to what trap is "best" for beaver.
The answer as to which trap an individual, me for example, would choose if he were given one choice is available as that is a subjective choice and is disjoined from the objective choice of "best"
What I would chose, given only one choice, would be the foothold trap. I would choose that because it's my "go to" device when I have to catch educated beaver. It will catch beaver when bodygrips and snares won't.
Endeavor to persevere.