Shawarma Debate - Chicken or Beef?

In What's on Your Must Try List? a little back and forth has started on the topic of this city's sandwich of choice, the shawarma.

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Dave said: It may be a bit of an Ottawa cliche, but a beef sandwich from Shawarma Palace is unmatched in this city, if you ask me.

And

David Reevely countered: Never tried the beef, but Shawarma Palace's chicken sandwich is the best I've had in three cities. If this were my list, I'd add it.

Sounds like there is a taste-off in the making.

What do you think - Chicken or Beef?