Typically, what I've seen is that with custom & semi custom cabinetry, the vanity table is a seperate piece with no base or legs. Because it's attached to the sides of neighboring cabinet pieces, you can make it any height you want. 35 1/2 must be the kitchen height cabinets because Kraftmaid's bathroom cabinets are 33in and other "bathroom height" cabinets we looked at were on average 31-32 inches but kitchen height was also offered. It varies and depends on the company. In otherwords, you can figure out what a comfortable height is for you and install it accordingly. The differences in heights will add some nice interest to the space.

When seated, the typical height is 29-30". This is standard table and desk height. if you wanted the vanity to be kitchen counter height (36" with counter) you can get a stool that is taller than a standard chair to sit on comfortably.

I like my vanity area a little lower than table height. I'm not at home, so I can't measure it right now, but I think to the top of the granite, it's 28". I don't have a lap drawer....just a decorative apron/valance where your legs go. I didn't go with a drawer, because I needed my makeup area to be very shallow.

You can see my 'makeup area' by clicking the link below. It's in the 'gallery' section.

Here is a link that might be useful: My 28