Yeah, dialogue is something you have to try. Even if it means probably lifting a few phrases from the canon itself (I tend to use one or two as a 'launching pad' for the dialogue in my stuff at times) it helps you to ground your work and have it as a bit of a guide. Ultimate Tony loves language, the whole wit and whimsy of it, while Ultimate Steve tends to be straight forward, almost brusque at times, but he's not a dummy. Like, he refers to Rip Van Winkle. He also tends to shout and be really jingoistic at times.