The nice thing about working in hardware is that coding is pretty straightforward - and not terribly exciting to see. It is usually a case of setting up registers to do what you want. Most compilers usually do this pretty efficiently anyway.

Why work with a less capable device when the only advantage may a slightly lower cost (perhaps less than a $1 difference). The higher end devices are far easier to use, have greatly superior performance/features - what's not to like.

BTW, the PIC18 has an 8x8 hardware multiplier (the PIC24's is 17x17). Even with a 40MHz clock, the PIC18 requires 4.0uS to perform a signed 16x16 multiply - the PIC24 with a 32MHz clock is still 64 times faster needing only 62.5nS.