Thank you so much for sharing with me! At the moment I don't own either styles just my neverfull mm, I had a speedy 35 in mono I had bought and then sold, due to it being too big, and didn't like carrying it at the crook of my arm.
What I carry depends on my day. If it's just me, all I carry is my card holder, phone, keys, lipstick, and that's it. Now if I have my 10 year old little brother with me, I carry my card holder, phone, keys, lipstick, a gameboy, an iPad Air, headphones, snacks, baby wipes, a brush, deodorant, and a bag of legos.
I'm really torn
I would get the Twice as a bag for when it's just you, because you could always use your neverfull for when you have to carry kids extras. Both are great and neither would be a bad decision though, as the NM speedy doesn't cave like the OM so could be used with little inside, though the Twice is less cumbersome in size.