...use HTToolBox to make one bootable and the other not, then if you want to boot from the other make the other one bootable and the original not!
That's a little tedious. I had both bootable and gave my main one higher boot priority. Then when I wanted to boot from the other, I selected it from the early startup menu.
Isn't having two seperate partitions with two seperate Workbench revisions a little complicated? I mean if you have another partition with your Wordworth or another with your emulators... what OS partition do they look into for C: Libs: MUI: etc.?
It can get complicated, but you just have to make sure the needed files are in both partitions (SnoopDOS can be vital!). I had MUI on my Work partition, so that wasn't a problem. For paths, I used SYS: instead of the volume name so there wasn't a confusion over where it was looking for libs, etc. and so I could disable one partition without it saying insert volume xxxx:
I really didn't have many problems having 2 boot partitions. Probably my #1 problem was the annoying double boot in 3.9 which sometimes caused it to boot back in to 3.1 - causing me to have to select it twice in the early startup menu.