Your example with 640kB and GUI on top of MS-DOS isn't really MACs being technically superior. It's more a question of age and where different products are in their product life cycle.

If you look closer, you'll notice that lots of hardware from the PC have moved to the MAC. Because the PC didn't stay with the 640kB memory limitation and the 8-bit PC or 16-bit PC/AT (ISA) busses. It had a technological bump around there until people figured out (with a little help from Intel) how to get the bandwagon unstuck. The initial Win 1/2/3 releases didn't work as they did because of lack of knowledge but because they had to make sure there existed a solution compatible with machines released before the MAC. At every one time, you have to release products that are most suited to the target users at that time.

Initially, the 68000 processor in the MAC was advantageous for its larger memory space than the 8088 chip in initial PC machines. But both the 60xxx and the PPC chips did make the MAC far underpowered compared to PC machines until they too switched to Intel chips. And PCI etc did move from PC to MAC. Many MAC machines have been absolute toys, even if well engineered and well designed. All for the reason that they got their technological bump when the 68xxx and PPC chips didn't scale as required.

The main advantage of the MAC has not been a technical one. It have been the level of integration possible when a product is designed and shipped from a single manufacturer who strictly protects their child from external interference.

The main problem with PC machines have been hw incompatibilities, lack of drivers for Linux, BSD, ... and lots of BSOD from Windows. Why? Because there are thousands and thousands of companies building peripherial hardware without releasing good enough drivers. And there are hundreds of companies building more or less compatible PC:s.

Another big difference is that MAC did a quite brutal upgrade of their OS when they got stuck, while Microsoft (having a much larger user base and less "fanboy-dedicated") decided to keep the compatibility with one main exception. The exception that programs playing directly with the hardware stopped working after Win98.

In the end, you can't really point fingers at technical excellence. It's a question of selecting one single supplier who limits what you can do, but makes sure everything fits together. Or going to the "open" market where the world is full of options, but you need own knowledge to make sure you don't get stuck. You wouldn't see any BSOD other than when a machine is broken or overheated if Microsoft was allowed to run on such strict hardware as Apple does.

I regularly bash M$ for some of their decisions. For example their tendancy to send out new functionality with new security holes and start to close the security issues first when the solutions are already out in the wild. But my second big critizism is basically that they want to do the same thing that Apple does: Take ownership of the computer. It's many, many, many times easier to ship an OS when having the ownership. MAC owners expects Apple to keep a firm hand on everything. Wintel customers are used to be able to fool around everywhere (even when most users don't have the knowledge to fool around without burning themselves).

People select a MAC or a PC based in expectations. Apple is more warm and cozy. The PC is more down to the metal. At the same time, Apple wants larger market shares while M$ wants more control. It will be interesting to see what happens 10 years from now. It takes competition and mass-market to keep the hw costs down. On the other hand, corporations might figure that Apple machines gets less support costs because of all the fewer options.