To refer to the subject - Ay 4th is way better imo. Why? I use Ay4th, Samui, Darui and LM in arena, and:

1. Im still able to get 6 paths rank

2. Can 1shot a ninja in 1st round with combo (when vs immunes, can get lucky)

3. Ay4th is 1st rounder, need to keep Ay3rd clean until round 2, and with LM 1st mystery I easily beat Ay3rd.

So, where is the problem? Well:

In case of both Ay, Han owns you, Masked Man owns you, dont wanna talk about Shisuis and Minatos Anyway, they are great for LM teams, unfortunately, LM lives his hardest times atm, so they both cant really shine...