The hammock is light for 1 person at 1.5-2lbs and is reasonably comfortable as long as the temps outside are warm. As soon as the temps drop you need extra insulation in the hammock which defeats any weight savings over a light tent. The hammock does give you more stealth camping options though.

If I could only have one shelter it would be my Big Agnes SL2 Seedhouse tent at ~3lbs it is a very roomy solo tent and sleeps men [6'] and my GF [5' 8"] comfortably enough I'd use it on an extended multi-week tour.

Having the hammock as a second shelter I use when circumstances permit is a nice option, but it's cold enough around here that often that wouldn't be the best choice and when I travel with someone else the tent is more comfortable without any weight penalty over two hammocks.

BTW - I also own a bivy and they are not that light - certainly not worth the lack of comfort or room compared to a light tent.