[Lilji]

I think if we are talking about chanting liturgies (Sutta's/Sutra's, prayers, etc.) than it may be beneficial to do so with the translation into your own language. But mantras should be recited as they have been taught to us, as this is the very essence of transmission. When reciting mantras, it is not so much about the meaning, but resonance of the syllables that have a transformable effect.

I thought the OP was about chanting mantras, but I see the discussion is also regarding chanting liturgies, prayers, etc.

For what it's worth, I do my practices in Tibetan, as this is the instruction I personally received.

Terma