Intel chips had better integer performance and PowerPC chips had better floating point performance, which is why Apple always used Photoshop performance tests to compare the two platforms.
Apple adopted Intel chips only after Intel replaced the Pentium 4 with the much cooler running Core Solo and Core Duo chips, which were more suitable for laptops.
Apple dropped Intel for ARM for the exact same reason. The Intel chips ran too hot for laptops, and the promised improvements never shipped.
The G5 in desktops was more competitive but laptops were stuck on G4s that were pretty easy to beat by lots of things in the Windows world by the time of the Intel switch. And Photoshop was largely about vectorized instructions, as I recall, not just general purpose floating point.
Yes, and when it became clear that laptop sales would one day outpace desktop sales, Apple made the Intel switch, despite it meaning they had to downgrade from 64 bit CPUs to 32 bit CPUs until Core2 launched.
The Apple ecosystem was most popular in the publishing industry at the time, and most publishing software used floating point math on tower computers with huge cooling systems.
Since IBM originally designed the POWER architecture for scientific computing, it makes sense that floating point performance would be what they optimized for.
Apple adopted Intel chips only after Intel replaced the Pentium 4 with the much cooler running Core Solo and Core Duo chips, which were more suitable for laptops.
Apple dropped Intel for ARM for the exact same reason. The Intel chips ran too hot for laptops, and the promised improvements never shipped.