I find them equally beautiful. I would just pick the one less expensive.

Your bathroom subfloor appears to be wood. You want a properly waterproofed subfloor for your tile floor for a permanent seal. Hire a true professional.

The pure white will be very crisp and clean. Go with it!

plain white

I do like the look of the marble tile but I expect that the plain white porcelain will be easier to clean and maintain. If you're not happy with plain white, maybe you should look at some light gray, cement-look options? Like these:

Gray hexagon tile

or these:

Another gray hex tile

Or a porcelain that looks like marble:

Marble Lookalike