Color?
Roland Eco Max is Epson ink, Eco Ultra is Epson ink....same ink...so if you compare colors with these two ink sets....the only differences is RIPs and Profiles.
The ValueJet head uses the latest Epson head and has a smaller drop size, so instead of Lc and Lm you use smaller droplets C and M to fill in. In my own personal experience with identical images and good profiles, customers cannot distiguish color differnces between the ValueJet 2606 (six head, six color like the 540) and a ValueJet 1604 with the newer single Epson head all using the Eco Ultra ink sets.
Alignments - color to color - are fixed in a single head, making alignments easier and more stable....