Because Google is more used in the area where I live, I choose to go with Google webmasters' tools because it will help in my SEO optimizations BUT Bing almost delivers the same. Both are robust reports that every SEO sensitive developer should use.
Both are useful, but my question is what are you using their webmaster portal for?
If you're using it to see what words you rank for, Google Analytics is a better angle. If you're using it to see where you have broken links, there's better tools. I guess I'd need to know what you're using the webmaster tools area for. Personally, if I'm in the webmaster tools section once a month for a client, that's about it.