Since Avengers: Endgame introduced us to an alternate timeline Thanos who ended up with a less experienced and haughtier persona, I thought this'd be a good question to ask. Also, when writing the script, the Russos distinguished the two by calling the main timeline version Philosopher Thanos, and the younger alternate version Warrior Thanos, so I'm gonna use those names. For me, it's easily Philosopher Thanos. Warrior Thanos isn't bad at all, and I personally think Endgame is a slightly better movie than Infinity War as a whole, but Philosopher Thanos is a much more unique villain, what with his solemn way of carrying out his mission as if he only does it because he has to. We even get to see him change and develop onscreen thanks to the death of Gamora. Warrior Thanos is certainly intimidating and interesting, but Philosopher Thanos is just more so.
What do you guys think?