"Steven P. McNicoll" wrote:
So which practice should be followed? The one in AC 90-66A which
provides reliable information to none or the one in AC 90-42F which
provides reliable information to some?

I've found a very helpful AOPA document that provides useful guidance on
this subject (and provides me an answer to your questions):

"Safety Advisor
Operations & Proficiency No. 3
Operations at Nontowered Airports":

http://www.aopa.org/asf/publications/sa08.pdf

It states:

"Pilots practicing instrument approaches at nontowered airports on a
VFR day should announce their position in both IFR and VFR terms,

"Frederick traffic, Seminole Three-Six Lima, RICKE inbound, four-mile
final, Runway Two-Three, Frederick."

VFR pilots will benefit from a little education about instrument
operations at a nontowered airport. Learn if the airport has IFR
approaches and, if so, to which runways by referencing the A/FD. Have
an instrumentrated pilot or instructor describe the approach
procedures and explain the phraseology IFR pilots use to announce
their positions and intentions.
....
If you know where the missed approach holding fixes are and how
instrument traffic navigates to those fixes, you’ll know where IFR
pilots are headed when they announce on the CTAF they are executing a
practice missed approach."

There is more relevant material (including advice on when a straight-in
approach is not recommended) but the document's recommendations appear to
be (to me at least) better than the too-brief recommendations in the two
FAA ACs referenced above. So my answer to your questions would be
"neither," and would follow the practice recommended by the AOPA document.