I have stocks of all three batteries (AW, Efest, and EH) in 18350 and 18500 size. My anecdotal experience is that the Madvapes EH don't give as much vape time as the AWs and Efests, but they're about half the price, so I'm not particularly disappointed.
Here's a post from the ZMax thread by ECF member
Morandir835:
In all my testing the efest batteries (18490 1100mah imr, and 18650 1500mah) did perform well, as well as the AW batteries of the same size and mah, but didn't last as many cycles under the same use and charging conditions. The 18650 2000mah and the 18350's were a completely different story. The 2000mah had a higher resistance than that of the AW cell, couldn't handle more than 8.2a of current being drawn (rated for 10a just as the AW 2000mah is), and after 132 and 138 cycles saw significant loss in capacity. Have two AW 2000mah imr that are 288 and 312 cycles deep, and both still perform almost as good as new. The 18350 batts the efest had a higher resistance as well compared to the AW (which means lower amperage output, more dramatic voltage curve), and where the AW is listed 700mah and with a hobby charger measured an actual 698mah, the efests are listed at 800mah, and the best number I saw with testing my 4 samples was 673mah. Again right ~125 cycles they started losing performance. How is saving that $1 worth having to spend another $6.59 after 125 cycles later, when I can spend the $7.60 on an AW 18350 and 200 cycles later still going strong?