I’d bet on the tiger. Bigger, stronger, used to operating as a solo predator (rather than a pride), etc.
Plus, tigers are just plain *cool*, so I have to root for ‘em. :-)
My bet would be on the lion. Not the Gir lion (the Asiatic lion found in the Gir forest of India), but the African lion that is larger. Why? Because the only purpose of the lion is to protect the pride from adversaries - usually other lions that, if they kill the lion, will immediately slay all cubs to make the lionesses get into heat. That's all the lions do ...mate and fight other lions trying to take over the pride, not to mention hyena packs (most lions that don't die of disease or starvation are torn apart by hyena packs when old and alone). That's why lions have manes ...protection from other lions, not to mention making them seem larger.
Virtually all fights between lions and tigers involved Gir lions vs Bengal tigers, which was not a fair fight. A fight between an African lion and a Bengal tiger (similar size) is a whole other matter, and my bet would be totally on the King of Beasts. Every single time.
Now, if you make the tiger the Siberian/Amur tiger then this conversation is moot. The Siberian tiger is simply too large.