They are two different animals and can't really be compared. There is a way to analyse price movement using OI, but as I remember from decades ago OI is announced only weekly, but maybe that's changed. If not, using such for short term trading would not really work. And, in any event, IMHO OI analysis is really just guessing what the longs and shorts are doing. I have no 'open interest' in it!!In futures, there is open interest besides volume. It puzzles me whether one should consider both open interest and volume in futures analysis. Which is more important consideration? Open interest or volume?
If you have to ask which is more important, I would guess that you have not given much study to volume. You may want to do so for a few months, and if you come to understand its value, you'll never enter a trade without considering it.