Probably Orcs & Goblins. They?re a very flexible army built to compete with basically anything. Note that you will want some Orcs with the rules changes and points changes in the new army book.
Dwarves are also a very competitive army, especially since their last army book came out, but they don?t give the most satisfying games against Wood Elves in my experience. In general, WE can?t beat a fully-ranked dwarf unit in HtH unless we gang up on them with three units. Sometimes not even then. So the preferred way to beat Dwarves tends to be to kill all their supporting units (the shooters and warmachines), contest the quadrants, and maybe fight one or two of the blocks towards the end of the game after they?ve been softened up and lost some rank bonus. Needless to say, this isn?t the most fun or exciting game for the Dwarves. Now, since the new book came out, they have been given the perfect anti-WE tool: the Anvil. The Anvil gives Dwarves an un-dispellable magical attack spell (WE are vulnerable to these, as they have low T, poor armor saves, and Forest Spirit ward saves are negated by magic) AND an undispellable movement spell. WE archers shooting you? Have a unit of Miners come on behind them, then immediately have it charge in the shooting phase! WE skirmishers moving around your flank? Turn to face them, then charge in the shooting phase! I?ve played one game against the Anvil so far and read battle reports of several more, and the Anvil is just devastating. Even if the WE player finds a good way to deal with it, it seems a trifle boring to have the game centered so much around this one uber-unit. So that?s the conundrum with Dwarves v WE. It seems tough to find that balance that leads to really good games.
O&G, OTOH, have so many unit options and different ways to play the army that you should be able to find multiple builds which can compete vs. WE without making it too one-sided.