Usually people go with axes, since the Berserker Axe is the best 1-handed weapon in the game and thus perfect for a lot of the sweet runewords. Overall it doesn't really matter that much, there are many excellent unique/runeword options available for both swords/axes/maces, pick according to what you've got.
Axes are better simply because beast cant be made in swords.
Since botd/grief+beast is the best combo in the game there is no reason to pick sword mastery. ALWAYS dualwield botd/grief+beast vs anything but other wwbarbs.