Your intended route
If your route follows pathways, you will be comfortable with sandals.
However, if you come off the pathways, breathable shoes are more suitable in terms of protecting feet from stones and plants.
If you do not hike often, opt for comfort.
If you go out frequently, you require grip. Opt for models with soles equipped with Cross-contact technology.
Type of terrain
If you intend to cross puddles or waterways, check that the sandals or shoes are water-resistant. If it's really wet outside, don't forget a waterproof jacket!
If you intend to remain on dry land, you can select more comfortable materials such as leather.