Can’t answer that one specifically, but I saw a documentary about someone trying to capture on film the moment when a tiger captures its prey/makes the kill in the wild for the first time. In it, an indian tiger discovers a bear in a cave – bear runs out, rushes the tiger which backs off, quite a lot of growling and standing off each other, but it was the bear that was the most aggressive, and eventually chased off the tiger (straight towards the cameraman who was sat on the top of a very high chair filming, which made for some v scary footage as the tiger runs straight towards you!). The bear didn’t appear to be defending cubs or territory as it ambled off in a different direction after, so on that note I’d go for the lion!
Ps – some knowledge from my professional that may be relevant – tigers and lions are so similar, it’s pretty much impossible to tell them apart just from skulls or fossils…