Vertical Chamber Round Balers

What is the supposed advantage of vertical chamber round balers over previous conventional designs?

 

I've got an old Vermeer 504L that has the horizontal bale chamber if you will, and it seems a lot less finicky than my newer 604M with the vertical chamber.  I'm wondering what convinced Vermeer to go with the vertical chamber on newer balers, it appears Deere and other manufacturers have been using it for some time.  From my experience, the vertical chamber balers rely more on belt traction to get bales started than the previous design.

 

Thanks.

Vertical Chamber Round Balers