I've never tried insulated shorts. The combos that I use, from warmest to coldest conditions are as follows:
- Bib shorts
- Bib shorts under jogging pants (not quite tights, but more snug than sweat pants)
- Insulated bib tights (ankle length)
Of course, there are several different combos for my upper body as well.
I don't see how insulated shorts would fit into this lineup, although I guess with leg warmers you'd have versatility for changing conditions.