93 is generally the faster route. Quite a bit of it is still only 2 lanes. While its all good road it is known to be one of the deadliest highways in AZ. Mostly due to people passing without enough room on the 2 lane sections resulting in head on's. Most days 93 is fine but on holiday weekends I instead take I-40 to Ash Fork then south on 89 thru Prescott (Use bypass to go around Prescott traffic) to I-17 and into Phoenix. It's about 40 miles further than 93 but mostly interstate so not much more time wise. More scenic and stays in cooler climate much of the way.
If taking 93 then it might be beneficial to use 74 south of Wickenburg to cut over to I-17 although this depends on where in Phoenix you're heading. This avoids traffic as 93 becomes Grand Avenue in Phoenix.