Despite all of the openings listed, I didn't vote because I don't mind facing any of them! Perhaps that is why I play 1. d4
I hate to face the Benko, but what I do is this:
That may be silly, but it would bamboozle him. now, while he got pawns to take, I'll safely 0-0 lol
In the Benko, I play the fully Accepted old Mainline and make Black prove their pawn
The Grunfeld I don't mind facing either, but admittingly there is a lot of sharp theory. I don't mind that sort of stuff, but I understand it isn't for everyone. Here is something you may look into for the Benko and the Grunfeld:
Forum thread I created on the Benko: https://www.chess.com/forum/view/chess-openings/what-is-blacks-compensation-here-furthermore-how-sound-is-the-benko-gambit-in-general
Forum thread I created on the Grunfeld: https://www.chess.com/forum/view/chess-openings/how-to-handle-this-grunfeld-line
Obviously, both threads only cover a few lines and not entire opening ideas (which could take entire books as some have written), but this is likely more than enough to get an idea or two
nimzo