Why 3 phase is preferred over any other phase power transmission? [duplicate]

Why 3 phase is preferred over any other phase power transmission ?

My instructor was explaining this topic in my Electrical machines class. And he mentioned the following points

1. In single phase, system there is double frequency oscillating component. So, it is not preferred.

2. In 2 phase system, there is no double frequency oscillating component. So, it is ok to use it. And it can be used to transfer 1.414 times output rating in the same frame size as single phase. Also, we have return neutral current which is 1.414 times the peak value which is not good.

3. In 3 phase system, we can transfer 1.5 times output rating in the same frame size as single phase. Also, we have zero return neutral current which is also a good thing.

4. In infinite phase system, we can transfer 1.57 times output rating in the same frame size as single phase. There is not much improvement from 3 phase so we went with 3 phase.

Now, I am confused with the thing how he got the values 1.414 for 2 phase, 1.5 for 3 phase and 1.57 for infinite phase and what does it mean by saying in the same frame size. Please someone help me with this concept.

EDIT: I want to understand how the 3 phase is 50% more efficient than 1 phase whereas infinite phase will be only 57% more efficient than 1 phase. I am not asking why 3 phase over 1 phase as that I have already mentioned in my question.