Both are impressive, but I'm partial to the modded McCormacks. I don't think you will find many SS amps better than a fully modded McCormack at any price.
As for the stock versions, Peter Moncrief reviewed both and liked them almost equally if you read his International Audio Review.
Personally, I would go with the older McCormacks (DNA .5 or 1) for two reasons. First, these are the models that can be modified and the full mods surpass the current production models. Second, the McCormacks are more preamp friendly than the Odyssey. I don't think a passive preamp is advisable (and definitely not optimal) with the Odyssey.
As for the stock versions, Peter Moncrief reviewed both and liked them almost equally if you read his International Audio Review.
Personally, I would go with the older McCormacks (DNA .5 or 1) for two reasons. First, these are the models that can be modified and the full mods surpass the current production models. Second, the McCormacks are more preamp friendly than the Odyssey. I don't think a passive preamp is advisable (and definitely not optimal) with the Odyssey.