Yeah, the wild is much different than an enclosure, in the wild your not fenced in, leopards will run from lioness's why wouldn't they run from a tiger. But in the enclosure, the wild leopard is forced to fight, its different. Cats by nature would rather not fight generally, the lion is of course different though.
Ive seen these very large tigers, mixed siberian I guess, and their big, the sheer size alone is going to produce enough power to destroy any leopard easily. But..., I think it may depend on the leopards as well, Ive seen several different leopards at different sanctuaries, there different sizes. I saw one male one time with a good size head and thick neck, really thick, now if that thing latched on to the big tigers throat and wouldn't let go, that could be a problem, that seems to be what the accounts show. But odd thing is we don't really have any accounts of tigers killing leopards of any size in circuses except both killing eachother. Yet we have a lion killing two leopards at once.