User blog comment:JAlbor/Wikia at E3 2012/@comment-178.101.79.22-20120523065731/@comment-4564231-20120523191551

As AssassinOfAus said, it's about personal preference. Personally, I stuck with the dagger and hidden blades all throughout the four games, especially in Brotherhood, where you can dual the dagger with throwing knives. Since the hidden blade this time flips into a dagger, it's win-win-win for me ;)

Also, the hidden blade isn't the only thing used for assassinations, Connor pulls off a few sweet aerial Tomahawk kills in the announcement and gameplay trailers.