I hesitated to comment because I don't have experience with marble in my mudroom but I do have a cleaning business so I am familiar with maintenance on many surfaces. Let me start by recommending a darker surface with texture. One of my clients has slate in her entry and it is phenomenal on maintenance. As for marble here is what I have found. Although it is gorgeous it can be slippery when wet and if if it is not kept properly sealed it can stain. The lighter the color the more often it needs to be sealed so there is some extra maintenance there. I am in the process of building a mudroom and my space isn't very large as well so I had the same question. After shopping for a while I decided on vinyl plank (faux)hardwood for several reasons 1) because it is a slight texture which will work for wet feet. 2) I saved money by installing it myself 3) it looks really nice. This next generation of vinyl mimics the real stuff 4) because I will have a long runner covering the majority of it so why spend a ton? 5) it is not as cold as many floor coverings which is a huge problem in my mudroom. I hope this helps, good luck!