Are you going Alliance or Horde?

If you go Undead, WotF gives you a "get out of fear free" card that's comparable to the Shammies. The Priest's Fear Ward gets consumed, so you'd want something else as well.

Between WotF, FW and Trinket fear is a non-issue and that's your biggest worry as a 'boxer.

If you're going Alliance, Shammies have a clear advantage with their Tremor Totems.

In fact, the truth is that shammies have a clear advantage anyway. I tried 3 Alliance discipline priests (I found I couldn't juggle the healing + shadow form effectively with a shadow spec, so gave up trying!) and they were great fun, but an undead rogue or well-played hunter makes embarassingly short work of them.

In short, then, if you're not worried about being perceived as "just following the crowd", Shammies are the way to go.