IDK, hard decision being that we have limited information on both ninja. I choose Muu FTW or "Draw." Why?
I would say that Muu is similar to Oonoki. Muu has a Kekkei Tōta - a combination of three different nature transformations being, Katon, Doton, and Wind. The three nature transformation gives him a advantage in battle. The Second Hokage has Suiton skills, which is weak against Katon, and Space/Time Ninjutsu, and with the Second Hokage Suiton Techniques ruled out, he would have more of a chance with Space/Time Ninjutsu, but it would be useless fighting a opponent who constantly moves throughout battle. Also, with Muu's Sensor Abilities, defensive/supplementary techniques, such as Body Splitting Method, could very well outmatch the Second Hokage Taijutsu and other Jutsu.
Of course, many would place the Second Hokage's Edo Tensei Jutsu into play. We don't really know how well he was at controlling or utilizing the Jutsu, but if he was to create Edo Tensei on a weaker scale from what Orochimaru and Kabuto usage was/is, than he could have a chance with the Jutsu. If so, then the Second Hokage wins with little to none difficulty.