ABEC ratings really do not matter with regards to yo-yos.
Citations:
http://www.minibearings.com.au/technical/precision/440/ This literally defines the tolerances of ABEC ratings
Curious about Terrapin products - #17 by kyo - Yo-Yo Mods and Maintenance - YoYoExpert Forums
bearings - #6 by kyo - General Yo-Yo - YoYoExpert Forums
Bearings are bearings, kids. At the end of the day, spending more money for negligible performance is not going to make you play any better, no matter what a salesman says.