That depends on what sort of walking you're doing and what your personal preferences are.
The great advantage of a very stiff sole is on very rough ground, jagged rocks etc. Walking on such surfaces in a soft sole for considerable distance will cause significant discomfort and even localised bruising to the sole of your foot. A stiff sole will protect you from this by spreading the load better across your foot.
However on softer ground many people seek the "barefoot" feel and wear the lightest shoes they can get hold of, preferring to feel the ground under their feet and be more sure of their footing.
Personally I keep a pair of heavy boots and a pair of light shoes to wear accordingly.
A few quick examples:
Rough rocky ground, this is hard sole territory, if you're out here in soft boots you're going to be very uncomfortable very quickly. You may also appreciate the support from a high boot on the uneven ground.
Smooth and easy going, you'll want a soft light shoe which won't tire you out so much. Not a lot of rock to worry about and fairly springy underfoot. Very easy going.
The high fells of England. A medium sole as there's a mix of soft and hard ground, but a high waterproof boot. No, more waterproof than that. This was taken around 500m altitude and that's not fog, it's the cloud that's raining on the valley below. This is a water based landscape and what you're seeing are marsh grasses. Put a foot wrong and you're up to your ankles in a bog, you'll always be wet. Waterproof above all else.
All photo credit: me
- High Scafell Pike (Great Gable and Kirk Fell visible)
- Low Scafell (Wastwater visible to the left, Yewbarrow in front)
- Yewbarrow (right, Red Pike left)