If the pool pump is hardwired, then this rule applies:
210.23(A)(2) Utilization Equipment Fastened in Place. The total rating of utilization equipment fastened in place, other than luminaires (lighting fixtures), shall not exceed 50 percent of the branch-circuit ampere rating where lighting units, cord-and-plug-connected utilization equipment not fastened in place, or both, are also supplied.
So if you want receptacles on a hard wired motor circuit, then it can only draw half of the circuit's rating (which isn't likely with most 120V pool pumps).
The light circuit would be a better candidate for the receptacle but be aware of the "unspliced EGC" rule when you lay it out. I pulled 2 EGCs when I did mine. The unspliced one went to the J box and another was used for the receptacle, switch etc. My pump is 240v. I figure the I2R savings will pay for the extra few bucks I paid for the breaker ... eventually.
680.22 (A) (3) "Dwelling unit(s). Where a permanently installed pool is installed at a dwelling unit(s), no fewer than one 125 volt 15 or 20 ampere receptacle on a general purpose branch circuit shall be located not less than 3.0m (10ft) from, and not more than 6.0 m (20ft) from, the inside wall of the pool."
I would say a circuit for the pool motor is not a general purpose branch circuit, thus the convienience receptacle can not be fed from that circuit.
With a 240v motor the loss in the wire will be less (increases with the square of current) A wet niche light required an unspliced ground to the J box (with a few exceptions). Since I was also feeding another circuit from this (the receptacles) it was easier to just pull 2 EGCs and avoid any confusion.