Six months ago I would probably have argued over proraso Green or Cella. Loved them both and are the only 2 tubs of soap I've finished since I started DE shaving which shows how often I used them.
However, in going out and buying other soaps since I've tried several which I feel are better, Tcheon Fung Sing (in their various guises such as barbiere di figaro), Le Pere Lucien, Fitjar Folgefonn, Stirling, Haslinger - all of which are excellent soaps.
However, for me, I Coloniali wins just about. Wonderful, complex scent, great slick lather and, for me, the skin care is amazing. I also like the very subtle cooling menthol that comes through, not a big frozen smash in the face like some, which I am quite partial to mind, but a perfectly placed, subtle effect which feels great.