Advantages:

• mostly not waterproof, therefore much airier, quick-drying
• often less, or "0" drop (*), meaning a natural standing and walking experience
• no lengthy break-in period, as materials are much softer.
• Grip often better than with traditional hiking boots.
• Cushioning is softer than with normal hiking boots, more comfortable walking on flatter sections or asphalt paths
• Fewer blisters, as the foot cannot overheat as much
• Foot is not restricted in its movement
  

Disadvantages of trail running or light hiking shoes

• less stability, the foot has to "work" more
• mostly not waterproof (see below)
• wear out faster (lifespan approx. 700-900km)*
• conditionally resoleable (only worthwhile if the cushioning and the rest of the shoe are still in good condition)
• for alpine tours only for experienced / trained users
• not as robust as traditional hiking boots
• only works if the rest of your equipment is truly lightweight.
  

Conclusion

As always, there is no perfect solution for everything and everyone, but for all classic long-distance hikes in summer, light hiking shoes are usually sufficient. Many classic foot problems can be avoided with these shoes; walking is significantly less strenuous and much more natural.

The shoes or the users reach their limits if you:

• are not trained,
• carry a backpack that is too heavy
• are in overly difficult terrain
• the weather is consistently wet and cold
  

Waterproof?!

I sold mountain and hiking boots of all well-known brands for quite a long time and experienced pretty much everything ;-).

For many customers, it's a must that the shoe is waterproof; many probably fear getting wet feet.

A few words about that:

For classic (long-distance) hiking, the disadvantages of waterproof shoes clearly outweigh the advantages. The foot swells more because it gets warmer in the shoe, you sweat more, the foot is constantly damp, which virtually pre-programs blisters. If the shoe is wet, it takes quite a long time to dry. From spring to autumn, feet can get wet, but with light, airy shoes, they dry very quickly, and if I'm still cold, I put on fresh socks.

For high alpine tours or in late autumn and winter, waterproof shoes naturally have advantages.

*1: Drop: This is the difference between the forefoot and the ball of the foot. 0mm drop is neutral; in many classic running shoes, the ball of the foot can be more than 10mm higher than the forefoot.

 

*2: Shoe lifespan: Even classic hiking boots are usually at the end of their life after this period; you just don't notice it as quickly, but the cushioning is no longer the freshest either.