It makes sense if you look at it that way:
1. what is the purpose
2. how much energy is consumed to active that

Let’s say the only purpose is transaction verification
Than you can compare how much energy is consumed to achieve that

Also you can make any blockchain „greener“ if it does more at the same time than just provide a payment option.
For example it could hold assets and security tokens.
Same energy but more action.

So even if you put the same energy in both , the one which offer more functionality at same consumption is more efficient