510 threading does have the most stuff. The slim 510 (manual recommended, Joye brand recommended to avoid reverse polarity clones) can use all of the standard resistance atomizers, cartomizers (the Boge ones are very nice), and 510-T atty + tanks, and need a 510 charging cable. The Ego can use both standard and LR (hotter, low resistance) atomizers and cartomizers (Boge LR 2.0 cartos are popular) and its fast charging cable.
Most mods have 510 threading so if you head in that direction your old stuff will still be compatible.
100mah is about 1 hour of moderate vaping
Joye 510 - 180mah (short life but has nice roomy PCC charging case at NoSmokeVA.com)
Joye 510 mega xl - 280mah (60% more charge, uses a non-roomy metal PCC)
Joye Ego - 650mah to 1300mah (buy Joye or Janty brand - original manufacturer, or Riva 510 is a nice clone)
See Cignot.com and Liberty-Flights.com if you are in the US (at LF press the 20% upper left front page, then shop)
I use 510 manuals (sealed threaded end - safe from leaks) and Riva 510. I have charging cables at home and at work on Rosewill 4-port 2amp USB to AC adapters, and the PCC when out (as well and carrying a charged Riva 510 750mah battery).