EP,

Those that keep up with Mars news have probably seen the following:

http://www.spacedaily.com/news/mars-odyssey-02e.html

"The maps generated from the neutron data will vary with the seasons because in the winter, as it is now at the north pole, it snows dry ice over the poles down to about 60 degrees latitude," said Feldman. "We will be mapping Mars' surface for well beyond one Martian year so we will get maps of its surface during all of its seasons." A Martian year lasts 687 Earth days, or about two Earth years. Mars Odyssey's orbit is such that the entire planet's surface is sampled in four- degree longitudinal increments weekly

http://www.space.com/scienceastronomy/solarsystem/odyssey_update_020301.html

Boynton said the northern hemisphere might contain similar amounts of water ice, but that won't be determined until it is summer there and the large polar cap recedes. The cap's seasonal component is largely carbon dioxide ice and it masks what might be underneath.

As far as the other conjectures go I know one pole gets much warmer than the other do to Mars elliptical orbit placing it closer to the sun at the same time it is tilted towards it. Can't remember which it is, but CO2 ice may completely evaporate from that pole during its summer season.

Regards,
Mark