What's the big deal about a vanity? This is another area of the home often overlooked as insignificant, but you rely upon it everyday to complete dressing and personal grooming. Therefore, assure comfortable use both standing and seated when planning the space and function of the vanity area.
Aside from washing your hands, imagine your daily routine and position outlets, towel hooks/bars, medicine cabinet, etc. within easy reach, and don't forget about bathroom clean-up and plumbing maintenance. You should also be able to accomplish those tasks from a seated position in order to avoid stooping or getting on hands and knees to shut off the water for example.