FYI....I ran a 6 (643 JD)row on this same machine for a few years before converting. My observations...

1) yes,  I am able to get more acres done with a slower 8 row, than a faster 6 row.

2) what I did not expect to find......my diesel fuel consumption went down quite a bit when running the 8 row.

My thoughts are....I am better able to keep the machine at rated capacity with the 8 row. And, most of my fields are 1/2 mile long (or 1/4 mile so I can make an entire round), which means I have more corn (bushels) threshed with 8 rows and spend less time dumping more corn on the ends, than with the 6 row.

Your results may vary.....

edit; for clarity