I hadn't heard of Other World Mapper. From checking it out, I think I like the style of Dungeon Draft better. I've messed around with Inkarnate some but have always preferred what I can do in Photoshop.

I've done a couple structure maps in Photoshop. It was a lot of creating shapes and working with lines/rectangles instead of just drawing with my Wacom, which is what I was used to. I think on the whole, I'd prefer Dungeon Draft. I've also thought about using Dungeon Draft for the base layout then exporting to Photoshop and painting/drawing on top, using it as a reference.