Interesting thread about what and how to carry. Messenger bag or backpack is personal preference. Backpack can definitely carry more, but if you prefer the messenger then so-be-it.

In my situation I found that carrying lots of gear on me anytime away from home was a non-starter for many of the reasons mentioned here. The backpack became what you'd take on a weekend hike -- way too much for EDC. Now I'm down to pocket carry for EDC.

My truck OTOH is always nearby -- home, work, shopping, traveling... The kit in the truck is good for quite a few days and includes food, water, coffee (w/ Ti French press), a light sleeping bag and blanket if I need to pull an all-nighter on the road (BTDT), hygiene items and large FAK. Tools sorta go with it being a truck.

If I didn't have a truck I'd have a duffel or container set up as a trunk kit. If you travel by mass-transit -- sorry, I'm out of ideas, back to your messenger bag.

As always, YMMV.