Timeframe of Pike and Musket is 1480-1700, though campaigns end later to allow even the weakest factions to rise in skilled hands.

MTW XL is medieval mod, PMTW is a total conversion.

Basically if you want a huge change in virtually all areas choose PMTW, it is also noticably harder to play with- if you want more medieval warfare MTW XL or BKB's mods are for you.