There were moments where PPC performance was acceptable or better than Intel, but they were brief, far between, and for most of the its life the PPC was far behind Intel.

Take the 867MHz G4 you mentioned. There might have been some applications where the G4 was beating a 1700MHz Pentium 4, but at the time of the demo the top-of-the-line from Intel was 1800MHz and they released a 2GHz only a few days later. A year later Intel was shipping 2.8GHz parts, and Apple was selling 1.25GHz G4s. So whatever architectural lead the G4 enjoyed, Intel was eroding it with faster clock scaling.

This does not even mention the mobile space, where in 2003 Intel was shipping the Pentium M, not the Pentium 4, and it was the Pentium M which derived from the Pentium Pro/II/III and foreshadowed the Core product line. The G4 had no architectural advantages over the Pentium M. Apple's mobile products were stuck on the dead-end G4 for years.

I owned a Mac of some kind throughput the PowerPC era but it was only because I had to run Mac applications. There wasn't anything good about them except on rare occasions you got to see the AltiVec unit really go crazy. Most of the time you just got to marvel at how slow and expensive they were compared to the other PC on your desk.

The G4 was where the rot started to set in, but people are forgetting about the 601, 603 and 604, which had themselves several years of history in Apple designs. The 604 in particular was a real piledriver for some applications and easily competed with x86 of the same era, and the G3's integer performance was even better (its main Achilles heel was a fairly weak FPU, but this wasn't a major issue at the time for its typical applications).

Initial G4’s were solid products, but it rapidly spun out of control as they tried to ramp up the clocks.

I ran a Powerbook 12inch as my main computer for 4 years while going through computer science study (i.e. doing some relatively intense assignment projects on it). While the CPU was slower I'd argue that the OS at that time made up for it - using 10.4 - 10.6 compared to XP and Vista was a breeze. I had 740MB of RAM that was very much under my control, the only background task I sometimes had to look out for was the search indexer. OSX Terminal was light years ahead of the crappy windows terminal at the time. PDF support across OS was applied to good use to create good looking reports.

Now the tables have turned though. MacOS software has suffered greatly while MS has embraced Linux and the Terminal. Win10+WSL+Windows Terminal+VS Code today is the superior toolchain IMO because it gives you access to the package managers that will also run on your target servers.

The problem is that both Apple and Wintel were fighting for consumer customers; people that were proficient enough to word process, email, and browse, but not proficient enough to understand chip architecture. They just see a spec and assume higher is better. If you have to start from a position of arguing that the your opponent's advantage is a myth, you're already at least a step behind.

Moreover, the enterprise market had lost that war already. Who cares if PowerPC was really faster? Intel was a cheaper chip that did the job. Everyone in my customer service, accounting, HR, etc department can have a PC for much cheaper than Apple.