I like Ence as a separate word from Exp for two reasons. First, Exp is very strongly tied to a meaning in games that is in important ways opposite from the meaning we would want Ence to have. And second, I don't think "exp" counts as properly monosyllabic; the monosoyllabic prononciation /eksp/ has a consonant cluster that many languages and English dialects don't allow in speech, causing speakers to automatically expand it to /ek.spi/.