This report from Michigan State University, tested four orchard systems and the expected yields. The trees are between 10-20 years of age, have 600 trees per acre.   According to these statistics, the 4-wire trellis system is expected to produce 10.5% less then Vertical Axe, V-Slender Spindle, and Y trellis.  Realistically, there is not too much of a difference between the trellis systems in terms of yield production.