Gravel

Although similar in many respects, gravel shoes are often lighter than MTB models, and feature a moderately stiff sole balancing ample power transmission with a degree of comfort when walking and hike-a-biking. They also have a less aggressive tread profile, enough to offer grip on mixed terrain without adding unnecessary weight and bulk. 

To combine breathability and waterproofing, look for shoes with membranes made of tech materials Gore-Tex®, which keep water out while allowing perspiration to evaporate. Choose seasonally-appropriate footwear that  provides good ventilation through strategically-placed vents that encourage air circulation without compromising protection against the elements.

Ultimately the degree of sole stiffness depends on the rider's preference. A rigid sole offers better power transmission, which is ideal for long rides or rolling terrain. However, a slightly flexible sole offers greater comfort on long bike rides, as well as for walking, and is beneficial for technical creek crossings or off-trail exploration. Most gravel shoes tend to have a moderately stiff sole to provide greater versatility.