I think "little" is a broader term than AB.
Obviously I can only speak for myself, but it's a term I love, and I identify as a little. But the glaring difference between myself and I suspect most others around here, is I am an older little. For me, my little self is around 9-12 years old.
I suspect most people (and yes, I am generalising based on stories here) see AB as an actual baby age, maybe up to 18 months/2 years or so. From there, most would define their little side as a toddler type age, perhaps 2-4 or so. I know that it's different for everyone and we all have our own twist on it, but as I said, generally.
But for me, I don't want to be that little. Bottles, pacis, plushies and stuff don't interest me, however I do still love diapers, and of course wetting. I recently commented on another thread about how intrinsically linked wetting is to my being little. I can't feel really little without some form of wetting involved.
A lot of people like to just chill and play with toys or watch cartoons and such, but for me that is only the prelude or the build up for little me to be putting off going to the potty when he knows he should. Little me is way too old to be wetting his pants, but he will delay it for as long as possible while he's distracted, and eventually be that bigger kid who wets himself.
When I incorporate diapers into my little time, it's usually as a result of bed wetting. My little is still wearing his night time diaper in the morning, or is getting ready for bed. Sometimes it may be a punishment for wetting his pants again, or preparation for a long car trip.
Occasionally I will get urges to be younger, but not very often. Even then, around 5 or so is the littlest I can feel comfortable being. I do understand why people like to be babied. Comfort, security, lack of troubles or worries, it can all be there for a baby, but I'm just too self aware to get there. Even with total privacy and an empty house I cannot just relax enough to get into a baby mode.
I have a "friends with benefits" girlfriend type relationship with a lady who is into age play as well. We don't see each other all the time, but when we do its to do some regression play together.
She likes to be babied, and her little is around 4. She loves to be taken care of, and have her nappy checked and changed, as well as baths and cuddles. Sometimes I play caretaker to her, sometimes a playmate. When it's my turn to choose, we are friends or cousins around 11, and both prone to occasional accidents or bed wetting. We talk about it and wear our pull ups around each other.
It's a weird relationship. We only see each other occasionally, and its planned well in advance, and only ever at her place. But it seems to work. I'll give her the little AB style fun she likes, and she'll give me the older playtime that I crave, although neither of us is really into the others fantasy so much.
And apart from our little sides, we really don't have a lot in common, and probably don't get on as well with each other as you would think. But it's an outlet that we share with each other, and it's more than a lot of people have I guess.