I think that other improvement is power consumption. Even with more RAM J728 consumes less. Battery life is:
J720 - up to 9 hours with 1,5 Ah battery and J728 - up to 14 hours with 1,95 Ah battery. So battery capacity is increased by with 30% while battery life by 56%.
Outlook is also different - some prefers J720, other J728. I do think it is easier to scratch top case of J728.
In general, I am for J728