I have a r90 and a r150 shallow. Really depends on what you are planning to do with the tank. I utilize the r90 as a mixed reef display and the r150 shallow is being set up as a frag grow out tank. The 16 inch depth makes it very easy to work in the tank, maintain, light etc and is very cool to look at from above. The shallow tank doesn’t look as nice from the front and if it were a primary display I would always favor a deeper setup.