In D&D (of all stripes), 'XP', pronounced 'ekspee', is the only acceptable shorthand for 'experience points'. In other games, 'XP' is never an acceptable shorthand for experience points, even if they are actually called 'experience points'. In other games, they may be called 'exp' (pronounced 'exp') or "E.P." ('ee pee') or "E.P.'s" ('ee pees'), but they are never pronounced 'eep' or 'eeps'.
This is observational, not proscriptive, on my part. Expect for the 'eep' part--'eep' is something you squeel when startled violently, such as being tickled by someone you didn't even know was there. It is not a word one uses deliberately, and those who do are silly. [Said in my best John Cleese imitation.]