I also have a fair amount of knowledge on geothermal energy. We can actually couple both; both help each other. If we tie a solar system to a geothermal system, you'll get more benefits from the geothermal system and you'll get good benefits from your solar system, so one with the other is very good,.
What I would say is that solar is certainly more applicable in the building and geothermal is more applicable around the building--if you dig into the ground, and so on--so the two compare.
If you look at one single building, what do you do? Do you look for the solar aspect of it? Could they be integrated architecturally? Geothermal doesn't need to; as long as you have land, you can dig. It's easy to do.
Sometimes it is more expensive than solar. Also, geothermal is very sensitive to installation--very sensitive. It's been said by the geothermal coalition, based here in Ottawa, that about 40% of geothermal systems work optimally, and the others don't--not because the technology is not mature, but because installation is not mature.
The same would happen in Canada. If we start going widespread now, at first the same would probably happen as happened in other countries with installation. The technology is there; the installation is sometimes more difficult at first. We do need some training.
If I compare both technologies, I would say geothermal is basically solar energy stored in the ground. You get it straight away from the sun, passively or actively, or you get it from the ground.