I use the green Superfeet insoles. They are expensive ($40) but I can put them in light hikers or even tennis shoes and they offer enough stiffness that my feet do not hurt. I just did a long trip (39 days) with LOTS of rock hopping and never had a problem with my low-cut Merrel hikers and superfeet insoles.

It is more important that the sole of your shoe be "sticky". An approach shoe has true sticky rubber - good for sticking but they wear out quickly. My Merrels have Vibrum soles with an aggressive tread - they work well.