I would have to say it depends on the encounter. If there is a lot of raid damage (including you) and/or movement, I would say
[Cowl of Winged Fear] is better because you have more stamina as a cushion and you won't miss the lower Spi since you will be moving around allowing for more OO5SR regen.
If it is simply standing still and healing pretty much non-stop, I would say
[Helm of Anomalus] is better.
The principles behind these choices can be used with future gear as well. In fact, this is the basis most people use when they fashion mana intensive gear sets vs raw healing power sets. As you progress even further, you may decide to enchant the gear differently with Spi or MP5 enchants instead of Spell Power on a few pieces.