Brevity. Clear enough? lol
If brevity were the driving force behind grammar, then we would adopt the Oriental practice of eliminating indefinite articles.
If you are getting paid by the word, then "more clear" is obviously a better choice than "clearer". In fact you would probably pull out your thesaurus and then go the route of saying that it is "much more precise". And if you are getting paid by the letter, you would say "significantly more precise".