Very apropos as I have just come from a community theater production of Carousel that could have used improvements in both.
In my amateur experience, pacing, or pace, would be the overall speed of the show. I enjoyed the musical numbers, but the dialogue scenes dragged; the director could have improved the pacing. Timing refers to the delivery of individual lines. The actor who played Enoch Snow had great comic timing; his delivery of the famous punch line, "Boston cream pie!" brought down the house. Timing is especially important in comedy. Bob Hope and Jack Benny are two comedians whose timing was legendary.