Myself, when I write in English, I write in English; when I write in Malay, I write in Malay. I find that different languages have different flavors, so to say. When it is translated, the taste is not quite the same.
For example, take the English word "love". In Malay, I can say "cinta", "kasih" or "sayang" which may seem to mean the same but are actually all different things.
A language is the product of the culture and history of the people who use it. Each and every word in a particular language refers to experiences specific to the people who use it.
For example, take the English word "eat" and compare it to the Malay word "makan". The word "eat" to an English person would bring up mental pictures of, say, steak and bread. To a Malay person, the word "makan" would bring up mental pictures of, say, rice and budu. So when the English word "eat" is translated into the Malay word "makan", the original meaning is somewhat lost in transit.
It is this reason why holy books which are translated cannot convey the same message as the original. This is also one of the reasons why the Holy Quran must be learned in the original Arabic language. We only refer to the translations to help us understand while we are learning the Arabic language.
Hope this is useful. WaLLahu aklam.