Well, you've heard a lot; I can only add that Whoopie slings are lighter, easier to adjust, will interfere less with the tarp ridgeline, etc. They're pure refinement!
I just got a Warbonnet Black Bird that had the straps, buckles and large metal caribieners...that rig seems to weigh a ton and was really bulky.
Whoopie slings feel like you woke up one morning to discover you lost 10 lbs over night while sleeping ;)
Gideon