Why does Edward prefer to use his automail over Alchemy?
He's trained in martial art by his master, Izumi Curtis. So he's definitely confident in his close combat ability. As to why he uses it over alchemy, you don't think he's just going to rely on alchemy all the time do you? He can adapt to different combat situation, and be more unpredictable if he can switch fighting style. Also his automail blade looks cool.