I have a 3 month old chunky butt.

She is my first CD baby. I got her one size FuzzyBunz (snap), small size FuzzyBunz (snap), BG 3.0 small (velcro) and 3 small Happy Heinies (velcro). All of the diapers worked with her but the BG was my favorite b/c the velcro was so easy to use. She's growing out of the small sizes so I bought some BG 4.0 one size w/ snaps b/c snaps are supposed to last longer than velcro. I'm not wild about the fit -with the FB one size, you can adjust the leg snap separate from the waist snap which is good b/c my kid has chunky thighs and a normal waist. The BG snaps only adjust the waist as far as I can tell. And the BG doesn't want to lie flat on the waist somehow... I can't describe it I should take a picture of it. I should've bought just one to see how I liked it b/c it is not my favorite - I like FB OS better. I don't know if the BG 4.0 velcro are similar to the 3.0 one size but I broke down and bought some medium BG 3.0 on sale.