I personally bought a 440 and a 523 battery for a friend as a present
For myself to play with, I might get a 250, though I've seen 350s/450s cheaper, which is weird because they're just 250s with a timer and different flash

The 100 is appealing, as the original pack camera

The one step doesn't have flash options

Ideally, I'd like to plug a flash into whatever I buy