Medvedev is the slight favourite in the match. He is the best player on hard court this season. He has won 49 times and only lost 10 times. If he finishes the ATP Finals as winner, he will become number 2. That should be enough motivation.
But Alcaraz is always good for a surprise. Very few people thought he would lose against Zverev. But in the same way, very few people thought Zverev would win.
It will certainly be a 3 set match. But I am not going to bet who will win the match.