Round one-for one this is an interesting match up and i like both characters but i think V would take this many people underestimate v and only think he is a braniac but in the comic and movie he has enhanced speed agility reaction time strength his intelligence is off the board he also is a decent martial artist, while Marv is a solid street fighter with great pain intake he relies on brute strength and as shown when he fought Kevin he couldn't lay a hand on him without prep V also has the same kind of damage intake and seeing in this is a random encounter v probably has his Daggers while Marv has Gladys(pistol) and his hatchet so if he uses all his rounds and shoots v and v hasn't dropped more or less Marv is a goner.
Round two-Even though V had years of prep in the Comic and the film i still believe he could use one week of prep effectively which includes crafting explosives reading more into combat arts which he already knows about also that he is bat Sh?t crazy and will win more often than not Marv's prep will be cruder and will not include things that are going to affect V as he isn't the brightest bulb in the box.
without prep marv snaps his sh!t up. marve crushed a guys skull casually and was rag dolling people across ra room. Marvs strength is above human level and his durability is insane. Marv will take a beating just to get an opening and once he does its lights out. with prep v would mostly take out marv maybe.