Hierro is a trail shoe, so the fit needs to work when the ground is not predictable. A little extra room can help on longer off-road efforts, but too much movement inside the shoe can become a problem on descents or uneven tracks.
The outsole is worth paying attention to as well. Vibram® Megagrip and deeper lugs are there for traction, but you still want the shoe to feel natural for the sort of trails you actually run or walk on.
Here at Smiths, we can help you compare the standard Hierro against the GORE-TEX® version. Waterproofing can be useful through wet grass, muddy tracks or winter conditions, but some people will still prefer the breathability of the regular upper for warmer days.
Bring in your current trail shoes if you have them. Worn lugs, toe scuffing and heel movement usually tell a good story about what your next pair needs to do better.