We go straight with the rows in no till for at least three reasons. it is the most efficient we to run tne divider between 15 inch rows using rtk autoguidance and we feel that the row of beans help by pushing each other through and over the cutterbar
where i come from in NC we cut at an angle because then the head is always flexing on our 2588 and when it gets damp it doesnt drag up hardly at all..and i had a buddy that runs a 2166 that was custom picking some of our beans and he was going with the row when it was getting damp, and the next morning when i looked in the field it looked like crap. so that is why we always cut at a slight angle
Normally, I cut with the row for a couple of reasons including that the dividers don't knock down as much of the crop and it seams like the row of beans will help push the beans into the augur to feed better. This fall though, I had a field that I was cutting for a neighbor and he had planted the beans in 30" rows to begin with but when he got a poor stand due to our heavy rains this spring, he replanted portions of the field with a drill. Never really seen this before, but where they beans were solid drilled it didn't matter what direction I went, but in the row beans, I cut had to cut them at an angle, otherwise it was like pricefarms said the field looked like crap because the field was slightly wet and would drag up instead of cutting.
We cut some straight with the row when doing contour strips, otherwise we harvest most on the angle. One reason two cut on the angle would be keep from pushing dirt on ridges left by planter or tillage when ground is damp, also in notill corn stalks like posted above. Most beans me cut are 15 in. or closer many times logged make impossible to put header point between rows.