I've already posted that, in my opinion, feeling comfortable with the text you are singing convincingly is more important. If you feel you can do an accent without going over the top, the dialect words present no problem and you are comfortable singing a song this way - fine. Conversely, if you're happier anglicizing parts of the text - fine again.
However if you're trying a heavier dialect like Geordie('Pitmatic' or not) or possibly a language like Scots (to say nothing of other languages) I think it's important that you also UNDERSTAND what you are singing about so that your performance carries the necessary respect and rings true.
If you're in doubt about the course to take, try making a recording of yourself singing the song in question with and without accent etc. and see which works better for you.