Of course, if the precedent in the game is that characters Hulk Out when they enlarge that's another thing... but I don't think I've ever seen a group do that.
If the caster can choose what grows, then the spell becomes much more powerful. But the DM has the final decision, so start writing down the out of the box interpretations.
Not that much more powerful. You could grow/shrink a guy out of their armor, which would be hilarious. You could keep their weapons from growing, but that's not going to make much of a difference.
The 1d4 bonus/penalty and advantage/disadvantage makes Enlarge/Reduce one of the weakest versions of the spell ever seen. You don't WANT to use this spell except for hilarity....such as polymorphing your Fighter into a T-rex and then enlarging him.
