Fritz from http://www.fritz40k.com has put up some great blog posts over time (2008 to 2012 so far). He’s an accomplished gamer, touting quite a few wins in the various editions of Warhammer 40k. He also has his own YouTube site https://www.youtube.com/user/WayOfSaimHann where he regularly posts videos about tactics and his experience with the current incarnation of 40k.
His latest post explains from his experience, they best Tyranid list and its features. It’s worth reading and if you want the proof, see his other posts on trying different ‘Nid lists in 6th Ed.