I much prefer sized nappies. I have a few greenkids, and similarly i didn't like them when my DD was younger (also a skinny kid) but i use them abit more now. I haven't seen Jazzy Buttz but we have itti bittis and BBH sized nappies.

I have one ittibitti tutto OSFM, but i don't really like it. Much prefer the fit of medium ittis on her. She is starting to fit the large ittis as well, but the mediums are still a better fit. SHe is 18 months and 10kg now.

Especially if you are planning on having another child, or have someone you can pass nappies on to, or sell them to, it is worth getting sized nappies.