Which save game does Red Dead Redemption load when starting from the main menu

Comparing to the better horses only, it beats the Kentucky Saddler in nearly all aspects (can't confirm speed). However, in terms of stamina the Hungarian Half-Bred wins and in terms of speed the American Standardbred wins. So overall a great horse but NOT hands down the best for you, try the other top horses to see if they fit your play-style better.

For reference: http://reddead.wikia.com/wiki/War_Horse, wikis are great for this kind of info in case you didn't already check.

I had trouble with dueling too. Perhaps try shooting where your crosshair lights up red. Also wait until dead-eye automatically engages and it tells you to draw. (?)

You can also try disarming the guy by shooting him in the hand. Some people, usually story related, cannot be disarmed, as such aiming for the hand will only get you killed instead, which can be frustrating.

Rockstar discussed it a little here, hopefully this is helpful: http://www.rockstargames.com/newswire/article/5991/rockstar_game_tips_dueling_like_a_pro_in_red_dead_redemption.article