This printing is identical to the first except for:
i) a deeper (3") box, and
ii) the rulebook is updated with errata.
[Source: Publisher product description.]
There are a few small modifications in the second edition:
"(1) Two units are added to the initial deployment. The blocks 3-Uesugi and 1-Uesugi-Gun get a circle deployment mark in the lower right corner, and two additional deployment circles appear in the Aizu location (which already had 3 of them).
"(2) The illustration on p.4 of the rules should be updated and corrected. In the original diagram, the stacks at Osaka and Aizu were incorrect. Now, the Aizu stack is further modified as above.
"(3) There is one error in the history section. On p.17, 4th paragraph, 3rd sentence reads: "But the early arrival of western troops had unnerved them." In this sentence, "western" should be switched to "eastern".
"(4) The chrysanthemum symbol that is used next to the title and throughout the publication is (mostly) anachronistic. The symbol(s) used, if any, should be both the Tokugawa and Ishida mon paired (for the two opposing sides) or the single Toyotomi mon (symbol of the past order)."
By deploying the additional Uesugi blocks at start, we follow history: Uesugi seemed a major force at the outset (having prepared an army) but later faded in importance (though spared a clash with Tokugawa, Uesugi were defeated by Date). All but one of the Uesugi blocks now begin on the board. This early deployment also challenges Tokugawa in the north, which is good for gameplay.
[Source: Designer Matt Calkins in forum thread titled "Sekigahara 2nd Edition"]