Correct, which is why those who converse only in ASL tend to be illiterate in written English. Without a one-to-one correlation between a gesture and an English word, there can be no written language beyond the most primitive level. I've seen the writing of many ASL users, and it is usually unintelligible.
On the other hand, those who use Signed English can usually make themselves clearly understood in writing.
Which one would benefit a child more, i.e. make him employable at something besides manual labor?
ASL is child abuse.
Deaf parents don't want their deaf children to excel? Can you really believe this to be true? Why not just say deaf parents don't love this children? And if that's the way you feel, why not just pass a law that all deaf people need to be sterilized? Get out of the dark ages!
ASL is child abuse? ASL is a form of communication. There is no reason someone can't be fluent in ASL and English. If they are not, you can blame their parents, themselves, and their educators. How can a language be abuse? This is a silly statement.
Those who converse only in Spanish, German, Japanese, and Chinese tend to be illiterate in written English, also. There is no one-to-one correlation between Chinese symbols and English words, but once-Chinese-only speakers are capable of having written language in English beyond the most primitive level. The same applies to ASL.
I know several professional deaf individuals who have completed college, medical school, seminaries, and other advanced education programs, and who write perfectly well and intelligible in English. Their skills in written English are well beyond a "primitive" level.
Now, written ASL does look very primitive to the average English reader; however, it makes perfectly good sense in ASL. The thing to remember is that this is not English - it is ASL in written form, which is something totally different.
On the other hand, those who use Signed English can usually make themselves clearly understood in writing.
Signed English is a bastardized, abominable version of signing developed for the deaf by hearing people whose only intent is to make the deaf more "normal." It has absolutely no correlation to signing, is much more difficult to learn than is ASL, and serves absolutely no purpose to a deaf person outside the classroom. Proper education by a person conversant in both English and ASL is much more effective in teaching a deaf person how to write effective in English than is trash such as Signed English.
Which one would benefit a child more, i.e. make him employable at something besides manual labor?
See my comment earlier. Deaf people are employed as doctors, preachers, teachers, and many professions other than manual labor. These individuals have learned how to compensate and overcome the difficulties in living and working in a hearing world, and have succeeded in their chosen fields.
ASL is child abuse.
Bull. Training a child to develop their full potential, to have the ability to communicate with a wide range of others - including other deaf people - is not abuse. Yes, since this is a hearing world, other forms of communication also need to be taught. But the value of learning ASL must not be denied.
To deny the fact that a deaf child is deaf, to deny that child the ability to interact with other deaf people, to deny the fact that a deaf culture exists and the child has a place in that society - now that is abuse.