That's the gist of it really. All of these apps are tabulating mostly the same forecast data.... there's some variation, but for the most part, you are getting similar results. It all boils down to look and feel. 1W looks pretty slick whereas a lot of the other apps I've used seem pretty dated and clunky.
Plus, there's a lot of layers of information.... The main pages have everything condensed into an easy to navigate and read, horizontally-scrolled format, but if you dig a little deeper, say in the extended forecast screen, you'll find those cool detailed NWS narratives for current, near, short and long terms, etc... those are nice for the science geek in me since it goes over weather patterns, fronts, trends, etc. Stuff like how a front way the hell out in Alaska will develop over the course of the week. I love that sort of thing.
Every other weather app just seems muddled. It's weather, it shouldn't be difficult.