I LOVE BumGenius 3.0! Honestly, I haven't tried the 4.0s yet, but I haven't fallen in love with a one sized diaper so I'm hesitant to try. We've used these for my son (who is now 3 and does not wear diapers) and my daughter is currently using them (she'll be 2 in December). They are solid and have lasted this long with no problem. Highly recommend them for someone who is looking! :)