I love these shoes. I have also been in the Vertical K and they are great but have become more of a hiking/scramble shoe than my go-to trail runner. The helios are a tiny bit stiffer and have a little bit more rigid upper making them great for varied and rocky terrain. They are still a minimalist style shoe with a low, 4mm drop but I feel there is enough body in the heel of the sole to accommodate the occasional heel strike on rough descents. They grip well on just about surface I have encountered, even wet rock that I have had trouble with in other shoes. I wear a 9.5-10 in most street shoes and a 10 in most runners. In the Helios I have the 44.5, or US 11. In comparison, I wear a 10 in New Balance MT110 and a 9.5 in North Face Hedgehog. They fit great, with a little extra room in the toe to help with toe bang on descents.