> a language with a larger alphabet will be able to express more > in fewer characters.

True, although it's not really the alphabet that determines this, it's the number of phonemes (distinctive sounds) in the language. For example, writing /s/ (the sound) sometimes with 's' and sometimes with 'c' does nothing to shorten words in English or Spanish.

But in general, languages with fewer phonemes tend to have longer words (and tone languages often have very short words---in a sense, they have more phonemes than non-tone languages). Morphology (particularly compounding) often obscures this.