Complex sentence: Depending on the purpose of the transliteration it may be necessary to be able to reconstruct the original text, or it may be preferable to have a transliteration which sounds like the original language when read aloud.
Split into simpler sentences: Depending on the purpose of the transliteration, it may be necessary to be able to reconstruct the original text. Or it may be preferable to have a transliteration which sounds like the original language when read aloud.