The early days of Marvel really weren't all that much different from DC in terms of story lenght. The stories pretty much were ecapsulated into a single issue. The FF defeated Mole Man and Doom in a single issue. The Avengers defeated Loki, Kang, The Commisar in a single issue. The X-men defeated Magneto, the Brotherhood of Evil Mutants and Juggernaut in a single issue and so on. It was later that stories started taking more than a single issue to tell and it was happening at about the same time at DC too. of course the two companies borrowed from each other other the years.
Now, while the heroes of the early MU had a bit more and different character than those of the DCU, they didn't really have flaws that we see in comic book characters today. Those they developed later. Tony Stark wasn't reall an alcoholic until the 70's, as an example. Henry Pym didn't really go crazy until the early 80's and the rest was a retcon. Wolverine didn't even exist during the Marvel Silver Age. So are you asking, what if starting in 1958, DC heroes were a little less white bread all American heroes? That is what the early MU silver age character were, but they weren't conisdered flawed at the time. That really came much later and DC was adjusting at the same time that way too.
So, what if Barry Allen had a temper or was impatient since he is the Fastest Man alive (look at presentations of Quicksilver)? Hal Jordan was over confident, since he was a fighter pilot after all? The Martian Manhunter was distant because he was an alien? That could potentially work for the newer characters, but for Superman and Batman it might not work, since they have 30 years of history to work on.
Torqumada