I have questions about this actually, because I see a lot of people saying this but personally I'm not seeing the difference.
If you basket pack a EQ and you vape it from low to high temps you can squeeze every last possible bit out of your herb before retiring it as ABV. Using the stock EQ parts I normally do 3-4 bags (if I'm doing bags) on one basket pack to make sure I get it all.
I think a lot of the "not efficient" stuff comes up because it seems like a lot of people are just throwing some stuff in the bowl or the basket and doing a bag and calling it good, which isn't really a fault of the EQ.
The only other thing I can see affecting efficiency would be making sure it gets from the herb to you without going anywhere else. The stock parts of the EQ are air tight (this surprised me, but you can verify it by take it all assembled, holding your finger over on end, putting it under water and trying to blow air in the other end, 0 bubbles) so the only place you could lose product to would be to the glass/whip/bag it self if it condenses on the inside.
With the stock parks, I can see losing a bit here. The stock elbow can cause some build up in the turn when filling bags, and of course the bag it self it just a massive surface area plus it stays in there a bit. With the stock whip, its got a tight 90 degree adapter that can cause some build up also.
All that being said, I seriously doubt efficiency lost due to those could be big enough to claim that "this vape is more efficient then this one" in any meaningful way.
Even if it is, DDave mod kit picks up the slack by fixing the lip in the bowl, bringing your herb closer to the heater, getting rid of the elbows entirely, and even offering even smaller baskets if you want to vape even less. Granted, that's a 3rd party thing you would have to buy and shouldn't be counted towards the EQ directly, but if you are concerned about what ever little efficiency you could be losing between the herb and your lungs, if CAN be addressed.
I see on here all the time though about how the E-Nano and Underdog are "SO MUCH MORE" efficient (not from you, you did not make a big deal of it like that, but others tend to). If anyone has insight on why it's more efficient I would love to know how, because I can't seem to wrap my head around it.