I do neither.

I begin the cycle doing five sets of five reps. Whenever I'm able to complete all the sets, leaving a couple reps in the tank, I bump the load a little. And continue to do so until I reach a stalling point.

Then, I just lower the load 10% and drop the fifth set. So, from now on, I'll do four sets of five reps.

When I get stuck again, I will deload and drop the fourth set. Sow now it's just three sets of five reps.

Rinse and repeat the whole process until I get stuck doing just one set of five reps.

Then, I start the whole cycle all over again, exactly at the same weight I originally got stuck doing 5x5.