Same theory behind small bong snaps vs loading huge bowls, a fully loaded plenty will give you tonnes of vapor, but it may be much more than you need which then suffers from diminishing return. For large groups, big bowls are perfect.
2L 4cylender hatch back will get you around just as well as a big V8 4x4 under most every day conditions, and use a lot less fuel. Only used a plenty once and a nano never but the "problem" as I understood it with the plenty was it needed a fair bit of herb just to get good vapor production going which is great if you want to load a whole gram but there are other desktops that will give you more of a single hit extraction with loads of .1 and under, which in my eyes is more "efficient" even though it's a subjective term.
To go further in the car analogy. MJ for me has huge diminishing return and most of the time I feel a certain high is achievable and anything past that is just chasing the dragon and doesn't really increase it, or increases it to a level that is not as efficient such as using three times the weed to get 30% higher for example (100% veryyyy subjective). If you are travelling 100km and the hatch back used 7L of fuel, the big V8 may use closer to 20L per 100km. The end result being the same, 1 hour later you arrive at your destination although 13L of fuel difference. To me .1 will get me high, .2 will get me just as high and so on and so forth, obviously vaping a 1gram bowl in the plenty will get you well and truely baked, but not 10 times as high as say 2 stems at .05 each in a log vape.