Either would work, so it's just a matter of taste. The dark vanity looks a little nicer, although personally I like drawers -- maybe you could get some good pull-out organizers for under the sink. I think dark is also a little trendier right now, but that could cut either way.

I would go with the mahogany one. I'm usually not a fan of it, but this seems to go better with your tile

dark one with the color of tub and toilet

Perhaps sharing a design from one of our projects will be of help? Here is one of our bathroom designs:

Custom Build: Bathroom · More Info

careful with marble..it's pretty sensitive to beauty products

I know many people who use marble. Apparently you need to make sure it's Italian marble and not from Asia. It needs to be sealed to avoid staining from the water.

Well, if the bathroom is a bathroom and you have kids or guests...go with a less stainable option for the vanity top. The cabinet style is always a matter of taste but consider the style of the other bathrooms and kitchen. What color and style are they? I do agree with the white option vs. cream. Everything will show with the white. I love the pull-out storage available for kitchens and bath cabinets. More storage the better. Guest bath needs a bit of everything your guests may need but are too embarrassed to ask for but need. Medicine cabinet with high shelves for aspirin and such items including those feminine items. I have been thanked for those little things that might have forced my dinner guests to leave early to fix. Your guests bring things with them that might spill and stain your vanity top too.

Both are beautiful, but I think beige would go best with your tile and it would be a nice transition from white you also have there. Something like this, for example.