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.