I have a leightweight 2 man tent and a silnylon/Eaglenest hammock set up. Both weigh about the same if I carry each full kit.

I will always prefer a tent for the simple reason that its generally faster to set up. Provides a greater variety of areas to set up, especially in the desert, and generally provides more shelter from mozzies and rain.

Plus I am a side sleeper and thats usually not as comfy in the hammock.