so.
there is nothing 'wrong' with leaving the leaves on, people cut them because they are full of chlorophyl and generally provide a harsher smoke than just buds. by cutting them and making hash, you still get to smoke them, but in a different form. Hash is cool!

comparing potency is hard to do. it depends on how covered the leaves are which depends on how well you grew the plant, and its genetics.

you can cut the leaves and just smoke them without having to make hash. it just won't taste super good.