The 1.5ml difference is not really a big problem for me. That OBS side fill will always win out in the end though.I do like the Ammit a lot too. Advantage OBS for capacity in my case, as I use it on a lanyard while doing weekend chores, like needing fewer refills.
When I need juice capacity, the Aromamizer Plus is always at the ready!

20ml's FTW!