I would not use the OTG as a mom bag because it’s somewhat heavy when filled, very structured, and does not have a lot of give when it comes to mom situations, like carrying a kid and a lot of stuff, squeezing in and out of cars, or stuffing the bag into a stroller. I suppose if your kids are older and you’ve moved past these stages, it might work out better as a bag to carry the extra kid stuff.
I use the All-In and I find it’s the perfect mom bag. Its size and structure is similar to the Neverfull but the straps are wider and therefore more comfortable, and it has a zipper top so when the bag topples over, everything inside does come falling out with it. I’m able to throw a bunch of stuff in there and there’s always room for more.
I also use the older Montsouris GM backpack on outings with the kids. It leaves me completely hands free and I don’t feel like I’m weighed down by a bag on one side of the body.
And lastly, the Speedy Bandouliere 35 is another great option. The bag also fits a lot, and the strap is great to use as a shoulder or cross body bag.
Good luck deciding. Ultimately if you don’t get another bag, you still have the Neverfull, which is a great mom bag already.