"All this being said, for most land navigation as well as ruggedness I prefer the SIRS G-150 or P-G M-73. Both are tritium prismatics."

They are very fine compasses. Personally, I'm of the opinion that there is no perfect compass with 100% durability or suitability to conditions. All have certain applications and certain disadvantages; it's a question of choosing the right type with the durability you need and the amount of hassle you're willing to endure. My W.F. Stanley/Francis Barker/M-73/Mk III/SIRS "oil bottles" are not map-friendly, and ALL have all developed bubbles with sharp temperature drops, despite the built-in diaphragm. They all use iso alcohol as a dampening agent, which in my experience is more subject to bubbles than those using light viscosity oils. I know one guy that filled his with marine compass oil to effect a fix and provide more dampening of the card. They're also heavy for what they do.

"These compare with my professional hand compasses for accuracy; Brunton GEO pocket transit and swiss merridian engineering/geological compass. These will set you back about $400-$500 plus accessories."

In my experience the 'oil bottle' prismatic compasses are accurate to about one degree or 20 mils, hand-held, when used in good light (the prismatic sight dates from the 1930s and is a bit dim) This is quite good, but I have a $5.00 Taiwanese liquid-filled lensatic compass that also provides this level of accuracy with no bubbles, either (though I wonder how many lemons I'd have to sort through to achieve similar results with a replacement). The Silva Model 54 can also be read to this level of accuracy in ideal conditions. Most individual compasses that purport to offer even finer readings and greater inherent accuracy usually need to be mounted on a tripod to provide consistent, repeatable results. That's just as well, since such accuracy is really unnecessary for general wilderness navigation. Even resection and triangulation position-finding techniques can be accomplished well enough with an ordinary baseplate compass to landmarks within normal distances, especially since there are nearly always ready alternatives for most of us with the availability of detailed large-scale topo maps and of course, GPS.

"The biggest thing in favor of the baseplate/mirror compasses is magnetic variation adjustment (declination for the non-aviator). While this is a nice feature, all mariners and aviators get by with protractors that do the same."

Right, but the point is it's one less thing to have to carry along, plus the declination adjustment feature eliminates the possibility of forgetting to make the necessary compensation (or doing so in reverse order) when cold, tired, or otherwise out of sorts. It must have value, as the popularity of these compasses has long since extended from recreational users to countless military, rescue, and mountaineering organizations all over the world.

"Plastic protractor baseplate compasses have to be protected in rough use, if you fall on one it's toast."

I'd have to disagree with that. Hit any compass just right and you can break it (especially the older oil bottle designs with multiple small parts and a glass dial face), but modern baseplate compasses are very durable and stand up well to most impacts - usually better than the U.S. army lensatic, which often bends the pivot with impacts onto hard surfaces. I've seen Silva 4's that survived being run over by truck wheels. Furthermore, I would expect many more reports of baseplate compass damage due simply to their huge popularity, not to mention the fact that a $25 lightweight baseplate compass might be in hand and in use a lot more, and not be carried or protected so carefully as a $150-$300 instrument. If you want an advance demonstration of ruggedness, Suunto used to test samples of their KB line by dropping them onto hard concrete from 1 meter height, not sure if they still do that (I'm not testing my $150 KB-77 that way, that's for sure). A lot of military forces have formally adopted the lightweight protractor compass and issue them (Silva, Suunto, or Recta) for active field service (U.K., France, Canada, Germany, Sweden, Norway, Finland, Denmark, Australia, etc., etc.). So far, the Eclipse design compasses have not found popularity either with the military or with the forestry/surveying market. At one point Brunton was marketing the 8096 GPS compass to adventure racers who liked the roamer scales, but recurring problems with worn-off markings and bubbles seem to have soured its appeal a bit, judging from comments by some owners.