Hi, of these options I would go for the grip. It's simply the most useful one in my opinion. My second choice would be the radio trigger, but for me it wouldn't be nearly as useful as a grip. (And I'm personally not interested in the other two.)

Regarding the grip, my opinion is that it makes shooting more comfortable regardless of orientation. The downside, obviously, is a bigger and heavier package to carry between shots.

Good luck with your decision!