Chris,

My point is that we can accurately calculate the stress due to the tides, and earthquakes are not strongly affected by them.

We can also calculate the effect of the oceans, and they are not second-order. Probably all the places with the largest tides have the largest contribution from the oceans, although a larger area of the Earth has smaller tides and has the solid Earth contribution being more important.

With regard to picking a particular mechanism or considering all of them, both have been tried in a rigorous way.

John