When it comes to moving large battalions on the battlefield, Tullius is more experienced, compared to Ulfric's previous experience of commanding smaller units against the Aldmeri Dominion. When it comes to guerilla warfare, that's Ulfric's strongpoint.
And yet it was quick, well planned ambush, and not large troop movements, that resulted in Ulfric going to the chopping block.
I'd actually argue that the difference between them is that Ulfric is the better politician, while Tullius is the better commander. I've never seen anything attributed to Ulfric that demonstrates any real tactical or strategic skill. In fact, he seems to favor a brute force approach. At Markarth, he didn't out maneuver the Foresworn. He blew them off the walls with his shout, then rushed the gates. He is, however, very charismatic and very good at getting people to follow him. He's also demonstrated a skill at political maneuvering.
Tullius, on the other hand, is an old military man and a general. He outmaneuvered Ulfric to capture him in an ambush and almost ended the war right there. He's also given credit for turning the war around almost as soon as he arrived. He is, however, not a politician. That becomes apparent when you listen to his conversations with Rikke. Here he is, trying to wage a war, but he's forced to play politics with the Jarls and it clearly frustrates him.