Difference Between M2S150TS-FCS536I and M2S150TS-1FCS536I from Microchip Technology

We are often asked the difference between the M2S150TS-FCS536I and M2S150TS-1FCS536I systems on chip from Microchip Technology.
According to the part number breakdown the difference is the speed grade seen on the snip from their product brief below.

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