When calculating properly, you will find on average the 18 series uses fractionally less codespace for the same functions. Quote:"16F877 wich was using 388 word of code space to a 18F452.... now using 722 Bytes" in this case 722 bytes is around 361 words.

I have not compared PBP's 18 series MAC and LIB files against the 16 series to see if they are identical or not, however given the same oscillator speed and configuration, I would hope to find the programs executed similarly, otherwise you will not have a direct upward migration path and compatability. There are of course salient differences because the archetecture is diffent to allow for features like increased program memory, RAM, etc. and PBP does take advantage of that because otherwise it would not work on those PICs. So of course there have to be some differences.