[Baron Spikey]

If it was a slightly more open battlefield then my vote would go to Chaos but with a significant lack of clear firing lines I believe the awesome speed of hormagaunts and genestealers will win out. That speed plus very little long range firepower being able to be brought to bear means the majority will get into combat if the 'general' is skilful enough. After Chaos Rocks has tied down the CSM firing lines it'll be the beginning of the end for the Fallen Angels.

I vote Tyranids