Celtic, fingernail, swept-back, O'Donnell, call them what you will, these gouges are those which have adopted sleek wings, removing the 'horns' seen on the upper most edge of traditional square ground bowl gouges.
Whilst their role in the process of bowl making remains true to their forebears, these gouges are approached and handled very differently. Capable of being used more predominantly on their side, these gouges can be used in creating a "draw-cut", that is to say moving the gouge in the opposite direction to that which is normally used, in an effort to more easily shape surfaces and remove material quickly and cleanly.
All this said, their use and effectiveness are very much governed by the user's tutelage and patience to learn how to get the most from these tools. In their basic format, they can and will achieve the same as that found with traditional 'square grind' bowl gouges. To see the real masters of these tools at work, be sure to explore the DVDs from Jimmy Clewes.