What are those shapes?
There are currently 2 different shapes used for a shaving brush.     
- Bulb Shaped
- Fan Shaped
Regardless of which shape is recommended for either bowl lathering or face lathering, keep in mind that a bulb shape or fan shape is a preference. Also, keep in mind that the knot and loft will influence the performance of the brush... Finally, some use both styles (Fan/Bulb) with the same size knot/loft and find the difference to be subjective in terms of feel with no real difference in efficacy. So, keep in mind that a Bulb or Fan shaped shaving brush is not a guaranteed success.
The Bulb shaped brush is rounder and has shorter hair around the knot. According to some, a bulb shaped brush gives more precision when applying lather. A bulb shape can add more backbone to a shaving brush.
The Fan shaped brush is more of a triangle shape where hair are the same length. According to some, those are better for face lathering. This type of shape will load better on a shaving soap as more bristles are kept in contact with the soap. Some will find it too floppy and dense (depending how high the loft is, of course).
- ^B&B Source - http://badgerandblade.com/vb/showth...hort-loft-Shavemac-users.?p=960946#post960946
- ^B&B Thread: Bulb shaped vs. fan shaped--which and why? - http://badgerandblade.com/vb/showthread.php/112724
- ^B&B Thread: Difference in Bulb vs. Fan shaped brush - http://badgerandblade.com/vb/showthread.php/196220
- ^B&B Thread: bulb vs. fan shape for face lathering? - http://badgerandblade.com/vb/showthread.php/138981
- ^B&B Thread: Bulb v. Fan - http://badgerandblade.com/vb/showthread.php/170935
- ^B&B Thread: Bulb vs fan shaped brushes - what's the difference? - http://badgerandblade.com/vb/showthread.php/145487
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