Most of the skateboard riders look into the ABEC rating before they buy, I don't blame them for trusting the ABEC rating, the ABEC rating is a very good indication that you are getting the lowest tolerance range (the lower the tolerance range, the higher the quality) but not necessarily higher speeds, in fact the speed relies mainly on the clearance, beside what most people they need speed should know the skateboard bearings are not fast at all, skateboard bearings usually spin from 1000 rpm (revolution per minute) to 5000 rpm, car wheel bearings are even slower.
The highest speed application I have ever experienced is for the dentist hand-piece that can go up to 400,000 rpm, they get their motion power from an air turbine.
If you look into ABEC rating, check the supplier and their "honesty tolerance", most of the imported bearings say ABEC7, ABEC9, ABEC11 and ABEC13 ... hahahaaaa ... that is a big lie, in fact that piece of information made skateboard bearings selling almost impossible for us (VXB) to sell.
If we sell an ABEC7 bearing, we have to sell $4 each with a very slim profit margin, surprisingly you can find a set of 8 ABEC11 or ABEC13 at $3.
Most common skateboard bearing is the 608, which has 8mm inner diameter, 22 outer diameter and 7mm wide, I don't think a skateboarder would need more than ABEC3 to achieve whatever needed, however, clearance can go to C3 to make bearing spin easier.
Don't you ever test a bearing with your fingers trying to spin them, that's an indication for nothing, long life bearings needs to be lubricated at the factory, which make it hard to spin by finger, having them dry would be better for that false test, but steel can rust, we had to sell dry (no lubricant) Stainless Steel bearing to overcome that false test.
Steel types are different, carbon steel is the cheapest (exactly like the fake imported ABEC13 ) we sell these @ $0.29 each, they are ABEC-1 and good for skateboarders that has $5 budget for a set of 8.
Another type of steel is 52100 which the most common respected material for the ball bearing industry, also Stainless steel 440C grade is good but not needed, and if you are one of the people that think Stainless do not rust, you are wrong, they do trust but have higher corrosion resistance. Also id you are one of the people who think stainless steel doesn't attract to magnets, you are also wrong, 440C didn't lose their ferromagnetism, however Stainless Steel 300 grades lost their ferromagnetism and became paramagnetic.
Last and not least the ceramic balls, in my opinion, ceramic balls can only be better if you go gravity downhill with no dynamic loads on the bearing, ceramic balls like the Zro2, Si3N4 are brittle and can easily be crashed, I don't advise ceramic balls (we still sell them though).