Definitely the Onza, the Yaabaa has a 20" rear wheel, which will make it difficult to upgrade, and won't feel very stable on the back wheel as the common 19" rear wheel on the bird. The onza also has a front disc which means the forks and the front hub will 'disc ready'. To get a disc on the yaabaa, you'd have to upgrade the forks, and the front hub. The yaabaa does have some nicer parts, but if you're just starting out your not really going to notice the quality of parts until you've been riding for a year or so. Bird.