The Thirsties Duo Wrap is almost a one-size diaper except there are two size options, so they fit well. I like the leg gussets, but I don't like the extra flap of fabric inside that holds odor.
Thirsties makes a Stay-Dry Duo Insert that's sold separately. It's nice, but the snaps are annoying as the pieces shrink differently over time.
I tried both the snap closures and the velcro. I did not like that the snaps were side by side at the top instead of up and down. It was always difficult to get them in the right snaps without skipping one in between.