Yael - I've just pm'd you in regards to a special on IB's.

In regards to snap ins vs sew ins, with the snap ins you can buy extra booster sets and just replace the boosters if the nappy is only wet, meaning you can reuse the shells, thats why I went for the snap ins.

I got one of the trial packs at the baby expo, which has both types, and both seem great to me!

You may even find that you DS and DD will fit in to the same size if your DS does need to wear one as my DD is wearing large in the IB, and she is only a few days older than your DD. I was told at the baby expo that the large should last me through to toilet training