I think perhaps some of the reason on why the PIC has gain wide recognition is due to the support of development tools.

I think the MPLab (free)is a great IDE which include an assembler, simulator and able to interface to 3rd party "C' compilers (HiTech, CCS and others), Microchip itself ICD as well as programmer. This allow any beginner to start programming and learning even without a physical chip.

Beside, there are lots of application notes available on Microchip website itself. In short, the basic information necessary to get started are located in a certalized location and not litter all over the place.

However, programming in assembly for PIC is slightly more tough than doing on a 8051 series due to the banking of memory which really can be a hassle. However, this can be solve using a "C" compiler where the linker will do the job fine. Beside, HiTech do offer a lite version of it's "C" compiler, thus, development tools for PIC is pretty quite complete, at least as a beginner.

Last but not least, my favourite still is 8051 although my selection is based on application, cost and other factors.

Best Regards
Andy