You didn't have an option to select "army list/concept" and so I picked fluff/fiction. However, I don't necessarily subscribe to all of the cannon fiction, particularly the grim dark emo wrist-slitting masturbation kind. I've got to enjoy some part of the narrative to the army for me to have the motivation to paint it. Hence my night-attacking Indians for FoW and "para" space marines
I paint slowly, so being able to add units to an army collection is important as well. Hence I tend to collect a smaller range of armies but have more units for them, allowing me to change things up as desired.
Painting for a tournament is the ultimate hobby killer for me - it feels too much like work. I resent the fact that I must meet a schedule and have to paint to a list. Painting to an army concept or core list idea is much more enjoyable for me and is more rewarding in the long term.