I agree with the bearing issue, but for the extra price, would the better material in the severe duty race bearings be better/worse for normal street use? Would tolerances be tighter or the same as "run of the mill" bearings?
The regular bearings are softer so dirt embeds into their surfaces easier so as not to scratch the crank journals. Typically race cranks are hardened and are less susceptible to scratching, so can use the more durable race bearings.
Tolerances are usually more dependent on the builder's preference than the bearing type.
