DS3 is definitely better with a controller and the DLC makes the game last around 20hrs.
Yeah I completed Dungeon Siege 3 using a 360 gamepad, control was very good. The game does look really pretty on a big tv, I had all graphics details cranked to the max. I played as Katarina, the girl with the shotguns, took me around 14 hours to finish I believe for the stock game. It's not a deep game, but it's definitely fun and worth it in the $15 range. I had also played Titan Quest and Torchlight and while I like both of those, I did prefer DS3.