Ah yes, the argument continues. Apple stopped using the Power PC architecture when IBM could not fulfill its promise on the G6 processor – the first 128Bit CPUs. IBM would have finished the G6 CPU 6 months later, Apple through Steve Jobs was not willing to wait. So he forced Mac development onto the Intel CPU.
 
The first prototypes of the Mac Intels used the P4 CPU. Compared to the PowerPC, it was slower than the PowerPC CPU when CPU Clock MHz were equal. In short, the Intel X86 (and later the X64) CPUs were (and still are) inefficient on how they handled their machine code. This has always been the case since the very beginning; as far back as the 1980s, a 1MHz 8bit 6502 CPU was 4X faster than a 4MHz Intel 8086 or 8bit 8088. The reason for this was simple – it took a 6502 1 to 2 clock cycles to execute a CPU instruction took the Intel 4 or more clock cycles execute. This waste still exists to this day even though clock cycles have been driven into the 3GHz range or higher.
 
The second set of prototypes used the Intel Core and Xeon CPUs. The Xeons were used in the high end Mac Pro and Xserve Server systems, the Core systems were used in every other system Apple made. But with the Intel CPUs, Apple also switched over to the mediocre Intel 950x GPU (Graphics CPUs) when before Apple used the superior ATi Rage and Nvida GeoForce graphics systems. For most Mac system, one could swap out the video with an ATi or Nvida card or add to it to one of the empty slots. Problem here is if you are using an iMac or Mac Mini system, you cannot swap out the video option as it is part of the logic board.
 
The Xeon processors were Dual or Quad CPU system, giving equal (for the Dual CPU) and superior (for the Quad CPU) over the G5 systems them replaced. The Core system depended on what they replaced; the Core Solo (a single core CPU similar to the P4) gave less performance over the G4 system is replaced while the Core Duo (Dual CPU) system gave superior performance over the (single core) G4. The one thing the Core Solo did was lower the price of Mac systems to under $1000.
 
Issues, problems?
 
The Intel system ran as hot as the G5 systems. But this is a given as any system running over 1GHz ran very hot, as any system running 500MHz require some cooling as they heated up over time. The Intel systems did drive the price of a Mac system down.
 
Upgrading can be a major problem. Though with most of the Power PC G4, one was stuck with what they got, at least one can upgrade other parts with minimal mechanical knowledge of how to get into the system as most system were easy to get into through a large access panel. Not so with the Intel systems. Many Mac Laptops were literally glued shut. Many Mac systems like the iMacs had self destructive sensors of if and when you open the case, these sensors would break apart internally. When one puts the Mac back together, it would not turn on or boot because these internal sensors determine if the Mac was tampered with and will not function if it were.
 
Given time Hardware Hackers figured out how to override the internal sensors and how to make a Mac turn on and boot without them. Eventually some upgrade secrets were discovered, though Apple does not approve of them.  
 
With Xeon based Macs (The Mac Pro and Xserve), one can order 0cta-Core Xeon CPUs from China and transplant them into the system, making a 2 – 4 CPU Mac Pro or Xserve into an 8 to 16 CPU system!
 
With the Core based CPUs (The Mac Mini and some MacBook/iBook Laptops) can have their Core Solo/Duo CPUs replaced with the Core2 Duo CPUs for improved performance and upgrade capabilities (Core system could only access 2GB or RAM, Core2 systems can access double the RAM). You need to check to see if your system board has a socketted CPU or a soldered CPU.
 
With being able to upgrade the CPU and RAM on a system to improve its performance, one can have a system can be viable for years to come. But are the older PowerPC G4/G5 system still viable today?
 
Again, Apple stopped using the G4 and G5 systems when IBM could not fulfill on the G6 CPU promise. This halts all Power PC software and OS support to 10.5. But similarly, older Intel systems have their software/OS support end at OS10.7. But is it better than PowerPC systems? As is – Intel has double the RAM of a G4/G5 system. But when CPU clocks are equal, the Power PC is about equal to the Intel in performance.
 
With the end of PowerPC Support ending at OS 10.5, also lost Classic (OS9) compatibility as of OSX 10.4. As stated on another thread, this might not be much to some but it is a major sticking point to others. A lot of the software today does not support software of the past. With the end of Classic OS Emulation, access to the older software no longer being made cannot be accessed.
 
Most are happy with the limited access to software that is out there for the Mac OSX. Some have taken their older Intel Macs and upgraded them to more viable systems with RAM, CPU and Firmware updates. But there are a select few die-hards that refuse to let go of their older PowerPC systems because the software they use does not have a compatible version within the modern system. I do not blame them. What good is having a “faster CPU” and Double the RAM of the older system when the software one need to complete a given task does not exist on the newer system? Many who have not thrown out or sold their older system will find themselves running to that system to run the older to access software not found on the newer systems.
 
For me that is why I have both. That is I always say that a system is as powerful as the idiot behind the keyboard.