The thing is, assuming you have a std box blade you can sure grade better being able to tilt the box forward-backward fully utilizing the front and rear cutting edges for both cutting and smoothing purposes.
The side link provides a whole different perspective for grading, that's why it is typically best to have both. The vast majority of people that only get one or the other get the top link.
You would use the side link more with your rear blade I would think. You can
get tilt on the rear blade using the top link. but you loose optimum blade cutting angle by doing so.
In your situation, only being able to control a single cylinder, I would recommend that you go with a top link.
But ultimately it is your decision to make.
Good luck with that decision.