Another option would be to use something like backupmenu to clone an existing unit without -thumb, and then ONLY update one of them. That would let you (after the update and a couple reboots for safe measure) do a true apples to apples comparison, including not only the kernel, but any updated executable that have been compiled for thumb that may be part of the base install and running. (Like browser and the like?)

That would, IMHO,be a much cleaner and "fair" comparison, and wouldn't require one to lose the active setup on their day-to-day device.