I use mostly MIPSBE stuff. When I update units from ROS5 to ROS6, I notice each unit uses approximately 7-9 MB more in RAM. I have many RB750 and RB750UP units in the field that contain 32 MB. They ran fine under ROS5. With ROS6, each unit usually has < 8MB of free RAM to work with. Also I notice funny thing happens when free memory falls less then 5 MB, usually result with a reboot.
I like to see that ROS7 use less memory.