Howling Wall is probably not a good choice.
There are 2 reasons why Howling Wall is likely to not help very much. First, low-fortitude enemies are less common than low-will or low-reflex enemies. Howling Wall is simply going to miss enemies more often than Winged Horde or Arc Lightning.
The second reason goes even deeper into monster statistics. You're interested in Howling Wall's repositioning potential? Well who's worth repositioning? Artillery & controllers have ranged attacks, so they don't really care exactly where they stand, while lurkers & skirmishers tend to have the mobility to just ignore whatever repositioning you do. Only soldiers & brutes are melee-focused (so they actually care where they stand) and lack the mobility to ignore being repositioned. Against soldiers & brutes, targeting fortitude is a terrible idea. Low-fortitude soldiers are very rare, and you can probably count on one hand the number of published brutes with low fortitude (by epic tier, most brutes' fortitude defense is higher than their AC). This means that Howling Wall is going to have an especially low hit rate against the enemies you're most likely to want to use it against.
If you really want to swap out Arc Lightning, I would look at Freezing Burst, Thunderwave (which, while also a fortitude-targeting repositioning power, is a more useful shape, has more forced movement, and has the easily-optimized thunder keyword), or Phantom Bolt (a will-targeting repositioning power; not much distance on it, though there are ways to improve that, but the psychic keyword opens up Psychic Lock in paragon tier).
If you can tell us what kind of wizard you're making, we can make even better recommendations for at-wills. For reference, here's the kinds of wizards:
- Arcanist (from PHB1; we would want to know what secondary stat you're boosting, wis/dex/con)
- Mage (introduced in Heroes of Fallen Lands; we would want to know which school you picked, enchantment/evocation/illusion/necromancy/nethermancy/pyromancy)
- Sha'ir (from Heroes of Elemental Chaos)
- Witch (from Heroes of the Feywild; do not pick this)
- Bladesinger (from Neverwinter Campaign Setting; do not pick this)