Some people have the opinion that there are differences in bearings but they would not be relevant as long as they are not defective. If a wheel spins 15-20 seconds without making a noise the bearings should be ok. The spinning time tells nothing about the behavior under load. A not serviceable bearing has grease as a lubricant needing to run in for about 50km and should be warm. A serviceable oil-lubricated bearing needs almost no running in time and spins better but has to be serviced! High quality bearings (100% european/us/japan made) should have a longer livetime and can make a difference for competitive long distance speedskating. But for inlinehockey the bearings have to stand the lateral stress caused by stopping and the sudden change of directions. So high quality low ABEC/ILQ bearings could do it better than more expensive midprice highend-bearings. I had the chance to get some greased SKF-ABEC5-skate-bearings (german manufacturer, 18 euro/16 bearings, online auction) and they are going into second season outside-hockey two to three times a week without any service.
But there is a big noticeable difference if you have high quality wheels beeing optimzied for your skating-style, weight, skating-surface and even the temperature of your rink. So spend your money for wheels and not for bearings.