Anyway, Looking at the specs on both of those phones and recalling some of my memories with the N97, I can't see why you even setting those two phones up against each others.
To be honest, the n97's looks like they are "dead" to Nokia now, and their lack of hardware power is impossible to do something with. And as you are comparing those two phones against each others, I guess the qwerty slide out keyboard isn't that important. - In that case, go for the C6-01 or something else. Stay away from the mini now.
Both phones have loud enough sounds, but the mini is a bit thinner in sound from loudspeakers, if that's what you ment...
JimmyIreland explained it above. The sound simply sounds thinner on the n97 mini. Weak bass, weak mids and lots of treble. However, the sound from music player through the 3,5 mm jack if you're using a decent head set is quite good. The loudspeaker on the n97 mini is perfect for ringtones with it's thin sounded speaker. It's loud enough if you don't have troubles with your ears, but then again it won't be better with the c6-01 either.
What I again suggest you to do, and what's best in any case is to visit a shop and try them out for your self. That way you will find which one of them suits you the best. In the end of the day we all do have different opinions
If you don't have any shops nearby or for other reasons cannot go there your self, please check out some youtube vids, read reviews (google for them). Gsm arena is one place. All about symbian is a place to check for reviews and lots of more. Again: Google is your friend.
Edit: Was writing when you posted your last one
