I'm going a different route this year with bare 18650 battery cells. Currently using a high quality Panasonic 3400mAh that weighs in at 1.61 ounces per cell.
Also have a single cell charger/pack for dual purpose use. With the cable its 1.77 ounces.
3 cells gives me 10,200mAh @ 4.83 oz
Charger w/cable @ 1.77 oz
Total 6.6 oz = 1,545 mAh per oz.
And that number will only go up with added cells if I want more power.
The biggest thing for me is using cells that are tested and proven out by a third party and are known to be reliable. Luckily the vaping community puts in a lot of testing on 18650 cells and has done the work on capacity and discharge curves. We really have no idea what kind of cells these companies are putting in their battery packs. They could be quality, they could be crap. Who knows?
This system as a whole, is a little clumsy and not waterproof like some. (A mute point for me because all electronics go in a dry sack) But I think the ability to add or subtract capacity, plus the fact if one cell fails I got more as backup.
Time will tell I guess, I may go back to a battery pack at some point.