The only problem with singlet suits is that if you do have a leak with the nappy you have to undress the baby completely to change the singlet suit and it can be a real pain especially if you are out or it is really cold. With a singlet you just need to change the bottom half with a leak which is much easier. I also found that if the singlet suit is a bit on the small side it can actually cause the nappy to leak so that's another consideration.

I used both and think it's a good idea to have a few of both especially at the start to see what works for you and bubs.