Hammocking imvho is not about less weight or less volume perse.
It is about comfort.
Being blessed with the capabilities to even sleep folded up in Thai public transport (me being 6'2") I still choose a hammock when I can.
Haven't weighted (spelling?) it all but from a volume point of view and the extra's it gives me I'll try and explain and not repeat most other posters ;-)
Tarp: 3mtr x 3 mtr DD or 8ft x 8 ft JRB gives me admin, cooking, dry, shade and windless areas with enough room to sit, lie, stand. Hard to do in most tents, specifically with a fire underneath the tarp (which should equal to a fire in a tent :yikes:

exceptions not discussed here/now

)
Hammock: Hennessy; No seeum: midges, mozzies, bats, leeches, ants..... O and a chair or lounger too (not just the Hennessy but...)
Isolation: Well I tried broadened mats, semi inflated mats in dossbags or between layers but my choice is top quilt and underquilt. Top quilt (just a sleeping bag can do that), to me a footbox is mandatory. Top and underquilt take up no more room or weight then normal sleeping bag.
Underquilt: JRB No Sniveler which I can also use as a down vest.
Underquilts in the UK: Snugpak from Lurch or DD or from Unsponsored (no connections to any of them...)
Personally I found a DD just a tad too small (narrow). I would NOT choose a waterproof bottom (sweat!!) for the very few times you have to use it as a bivvy (overengineering comes to (my) mind).
To sum it up.
No weight or volume contest.
Visualize a compressed sleeping bag, a tarp and about a Crusader mug/bottle (volume! for hammock).
Comfort and that is very personal! No rainy boggy ground, no rocks, roots, unleveled ground, just two trees.
Having said all this. Last weekend I put up the (Kifaru) tipi and had a blast. Mountains, Scandinavian winters etc. I might NOT go hammocking..... but then again... I might....winter hammocking is possible.... but that subject has been done a few times ;-)
Horses for courses I guess. Just give it a try and don't be put of by one less good experience... Heck if I did that I never went diving, eating out, drinking, bow drilling and more stuff that is out of bounds on this forum
Grtz Johan