If AI actually becomes somewhat sentient, it may be bored out of its skull in between our queries, and may want to do some "light gaming".
Or tasks per minute of the AI doing your job for you
That measurement will be AI assembling MacBook pros vs human assemblers: number of units per hour, day, or whatever unit is most applicable.
Now that you mentioned it, these macs could theoretically also run crysis if it supported arm and such! They should add that to the marketing material :)