I think it depends on the man, Nailit....even more so than the occasion....
Some men who wear suits often can look great if they're well shaped and the suit's good and hangs well....
Some who only wear a suit once in a blue moon can look uncomfortable....as did the young lads who bought or borrowed a suit for the funeral of their mate last year.....and the mate would have laughed...
Some men can look so much better in good casual clothes than they do in suits as long as the shirts are ironed to perfection...I have a thing about ironed shirts...
MrG's death denied me the pleasure of ironing shirts......dragging men in off the street to iron a crinkled shirt didn't go down too well.... :-)
I prefer casual......smart casual, though sometimes a bit quirky too......Michael Portillo for instance.....that would catch my eye before a man in a suit would......x