I was actually doing a tonne of research back in April on Martens vs Solovairs. Ultimately: go with Solovairs. I've had mine since April and have had 0 issues since finding the right ones and getting through the break-in period.
A few of my notes:
- Go down 1/2 a size. I recall reading a Reddit thread where users said to go down a full size. I wear a 10, but a 9.5 was the right size for me. I did have to exchange mine, but it was free so Injust had to wait
- There definitely is a break-in period. The shoes will be a bit uncomfortable, but shouldn't be unbearable. Once they're broken in - a week for me IIRC, they're a dream
As other lemmings have mentioned: Martens used to be good. But something happened, Martens switched to cheap labour & cheap materials, and a lot of the original workers left & started Solovair.