^ You'll notice the floating rotors don't have curved or diagonal spokes because the fasteners actually allow the outer disc to expand and contract, and also arrests heat transfer. This prevents or minimizes the risk of rotor warpage.

I think the Shimano center-lock rotor design kinda in-between a one-piece and 2-piece floating design. Some of the Shimano rotors are riveted to the alloy center so it would allow rotor spoke movement when the outer disc heats up and expands and so therefore reduces stress on the metal.

I don't know if it really matters in the end, because I haven't seen any one-piece rotors explode or crack even. I prefer the simplicity and the interchangeability of the universal 6 bolt standard rotors.

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