We used quartz for our vanity top, and I'd highly recommend it. No sealing, so staining, everything just wipes right up.

Marble is more porous and susceptible to staining. I can understand the desire to go lighter in the bathroom. We too have dark granite in our kitchen and wanted something more fun upstairs. Granite, even the lighter stones is going to be the best option. Quartz is another good option but it can burn (think curling irons) where granite does not.

IMHO, Sealing should really not factor into the equation, it takes 20 minutes to wipe the stuff onto the stone and buff it back off, and it's only needed once a year, if that, so what's the big deal?

we have granite (a dark) as vanity top and tub surround, shower bench, etc...it's great because it can withstand anything...wipes up beautifully all the time!
i would be always be worried about marble (as i said in another post, urine 'splatter' has marred/etched our sealed polished marble bathroom floor (though that wasn't a problem in a previous house we owned where we had lots of little boys around constantly, so maybe it just depends on the marble used...??)

Thank you for your feedback, very helpful.

sas95 - Yes, I know that quartz should be among my considerations but I just like the random look of natural stone.

lukkiirish & busybee3 - you have confirmed my hunch that marble is more prone to damage. I like the "upscale" appearance of marble but feel granite is the right choice. And I agree with lukkiirish that sealing is not an issue.

If you like marble, but want granite...

We are going with super white granite (white fantasy) for the vanity top. It is currently coming in very gray from Brazil and I actually like that.

Super White is a granite that looks very much like a marble but it's harder. It's going to be polished, not honed. Planning on sealing it good and hoping for the best!

Here is a link that might be useful: Super White Granite