I have been doing some research and predict that the panthers will win this...
https://www.quora.com/Who-will-win-...ce=google_rich_qa&utm_campaign=google_rich_qa
Who will win a fight between Black Panther (Bagheera) vs Bengal Tiger (Shere Khan)?
To repeat what the other answers said, Shere Khan takes this 10/10.
Bagheera, an Indian leopard, is extremely strong for his size
[1] , being able to overpower a Himalayan brown bear (7 feet in length) which weighed 450 kg, at least.
Bagheera can reach speeds of 35 MPH, matching Shere Khan in that factor. Bagheera is also fairly intelligent (knew the human child would be in danger as long as Shere Khan was around) and is much stronger than your average human.
Unfortunately for our leopard friend, Shere Khan is a massively strong Bengal tiger.
[2] . He survived being struck by a stampede of buffalos, each of which were over 650 kg, or 1000 lbs. He casually drove back several fully grown wolves, a bear, and other creatures with ease.
Another thing to consider is that in the movie, while Bagheera momentarily stood his ground against Shere Khan, it took no more than 30 seconds for the tiger to trounce the leopard.
Ultimately, whether you consider the book/movie lore, Shere Khan wipes the floor with Bagheera.
Footnotes
[1] Bagheera (2016)
[2] Shere Khan (2016)