Depends.
It's not an easy answer. Probably the first step is to look at lowering consumption if possible. If you can reduce your power needs on tour you need less of a solution.
Second, you need to balance the style of touring you are doing with the mode of charging. Currently there are three main ways: from the grid, solar and dynohubs. Each have their pros and cons. Whatever the choice, the most efficient mode of charging is to have a battery that you can charge initially and then recharge other devices from. This allows you to set and forget instead of cycling each device through the charging device throughout the day.
The grid is the most reliable if it is available.
Solar is weather dependent.
Dynos are distance dependent.
While a dyno may seem more applicable one has to also weigh whether you need charging for other activities (Camping, canoeing, hiking) and whether one is only using one bike for touring. I cycle, camp, kayak and dive and use both a 26" mtb and a 700c road bike for tours so I want a multi use solution instead of a single use solution. My solar panel works great in the summer and I feel I can be completely independent of the grid with my panel on the bike as shown in the picture above but it would be far less efficient during shoulder and winter seasons.
Last edited by Happy Feet; 11-01-17 at 12:24 PM.