Which one is better: delaying salah until we do it in the mood or forcing ourselves to salah and feel compelled to do it? And why?
I would say doing it as soon as the time comes in is better because the Quran says:
The prayer is a timed obligation upon the believers.The Quran, verse 4:103.
An important part of the prayer is to subdue the ego’s desires and break one’s routine for the sake of God. Doing this as soon as the time comes in is the best way to achieve it. As for how you feel about it, this is not as important; the point is to be able to force the ego to perform this act of worship regardless of what the ego wants. I believe this is the best way of proving to God one’s submission and eagerness to please Him.