Best DOS for each model

I have a strange fondness for the radio shack computers. What DOS does everyone prefer for each model?

I like TRS-DOS because that's what I've used on the III, 4 and early 16. Here's my list of OS's for models I have (or in the case of the 16a, had).
Feel free to add on or make snarky comments.

CoCo 1 - RSDOS 1.1
CoCo 2 - RSDOS 1.1
CoCo3 - NitrOS-9
Model I - No preference. No real DOS experience with this one.
Model II - TRSDOS 2.0a, because it isn't CP/M.
Model III - TRSDOS 1.3 (used this in high school)
Model 4/4p - LS-DOS 6.3.1
Model 12 - TRSDOS-II 4.2
Model 16a - Single User - TRSDOS-II 4.2
Model 16a - Multi User - Xenix 3.2 (if you did the PAL upgrade).
Model 16B - Xenix 3.2
Model 100/102 - Built in with a NADS box
Model 200 - Built in with a NADS box
Model 600 - Built in - not applicable
Model 2000 - Only ever used MS-DOS 2.00 (there is a Xenix for it, but I've never seen it)
Model 6000 - Xenix 3.2

I didn't include ANY of the clones intentionally. Feel free to do so.