I know this thread is old, but OP, what did you end up doing? How does it look? I am going through an eerily similar dilemma with my own bathroom reno!

Unfortunately, I haven't done anything. My sister works with a design firm and says that they use marble flooring all the time for clients. They have not had any issues. My biggest concern is rust in the water which I don't know because the well hasn't been drilled yet. However, my husband has encouraged me to go with the marble - he knows it's a look I love. Home Depot has the porcelain hexagon tiles but it doesn't look the same with the marble. I have two more weeks before I have to make a final decision. The pricing is good at The Tile Shop. Good luck with your project. I would be interested in hearing any ideas you come up with. Cheers.

I am doing porcelain penny tiles on the shower pan. Originally was going to go with white matte from the tile shop but now our contractor is suggesting something dark, which I don't want, but I am thinking of doing either the light gray or the gray/white combo (same ones you chose!) as a concession. I don't want the bathroom to be too white.

We were originally going to do marble on the bathroom floors (everywhere beside shower pan) and a marble counter, and nixed both of those. We are now doing porcelain faux marble on the floors and white quartz counter. The only place we still have real marble is the shower walls. I'm somewhat hesitant to do even that... But like yours, my SO says we should just go with it.