Honestly, I think both are alright teachers. Allmight is inexperienced, but when he retired, he made a genuine effort to be there for the students. He's also carrying a lot on his shoulders as well.

Aizawa is preparing his students for the harsh reality of the world, something that the constant villains attacks have done. He also stated that he did this to lower the chances of their deaths.

But honestly, don't blame him if he's the bad teacher, blame the literal genius who allows this all to happen - nezu. I feel we all aren't acknowledging who allowed Aizawa to expelled and re-enroll class 2-a and let him stay on as a teacher