Good post.

I usually try to use the lightest/smallest pack for the job and I'll usually strap stuff outside unless 1)I'm bushwhacking or 2)I expect prolonged rain.

On trips where I'm carrying a light shelter/groundcloth, that item usually remains outside for four reasons: 1) It's light but bulky, 2)It's usually the first thing I unpack and the last thing I pack 3)It can be dirty/muddy at times and 4)Quick access if a sudden storm hits.

On long trips with a canister I'll start with stuff on the outside. Then as my food is consumed I'll rearrange and move inside items to the canister and move outside items inside.

Anything I strap outside has a backup attachment point. Usually if it's in a stuff sack e.g. tarp or jacket I'll tie the cinch cord around a pack strap....just in case it comes loose.