<p>Does anyone have links to documentation or guides on making the decision between REST vs. SOAP? I understand both of these but am looking for some references on the key decision points, eg, security, which may make you lean towards one or the other.</p>

Google first hit
seems pretty comprehensive.
I think the problem here is there are too many advocates of one or the other, may be better of googling and getting more of a handle of the pro's/con's yourself and making your own decision.
I know that sounds kinda lame, but ultimately these sort of design decisions fall down to the developer/architect working on it, and
99% of the time, the problem domain will be the deciding factor
(or at least it should be), not a guide on the net.