Both great at what they do, but they do tend to leans towards certain things a lot that they excel at imo. Joaquin is the master at playing weird/unstable guys, Leo always brings his 110% intense yelling effort game (idk what to call it lol).
Bale was the lead actor in a Steven Spielberg epic and garnered universal acclaim for his performance back in 1987! That's crazy lol Though he did have a very under the radar 90s output.
I shouldn't have said easy but I feel like there's only a couple locks and the other spots are up for grabs. I feel like supporting is even tougher: Pitt, Pacino, Pesci, Hanks, Hopkins, etc.
Bale is incredibly well liked in the industry, his film is very well liked/well reviewed and has come out later than some other contenders. He can easily get nominated in lead.
Ken Miles has a very unique voice (kinda weird really) so I doubt it will be his actual accent. It will be strange hearing him use a British accent again though.