Figureing XP for an odd encounter

[Nail]

Half XP for the encounter because of the favorable set-up?

No.......provisionally.

Did the DM "help" the PCs along, by providing a convenient ambush spot and lots of clues as to it's use? The point is that if the situation of the PCs is "plot driven" as opposed to "PC cleverness driven", there might be less XPs to hand out. The distinction is "Is the EL inherently easy, or did the PCs just plan/execute well?"

IMO, the EL of the orc hordes charging across the bridge is less than it might be otherwise.....barring knowledge of the other circumstances Crothian added later to his discription.
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BTW, let's get some things cleared up: "CR" is what determines XP, not "ECL" (Effective Character Level) or "EL" (Encounter Level). The confusion with this usually comes from a quick skimming of this sentence:

"Adjust the XP award and the EL depending on how greatly circumstances change the encounter's difficulty." (DMG, p.39)

Note how the circumstance changes both the XP and the EL. ...Rather than the circumstances changing the EL, which in turn changes the XP. Got it?

 

[Nail]

I would award PCs exp for whatever they killed, however . . . .

Whereas I might not.

You get XP for overoming challenges. Killing or not killing is, in the end, irrelevant. Was the challenge overcome? Where the orcs defeated?

It seems as if the answer is a big, fat "NO".