Yes as far as I am aware, the absorption of photons of the correct wavelength by the magnesium atom leads to the ejection of electrons in a similar fashion to the photoelectric effect. Electrons are stripped from water to re-reduce the chlorophyll.
I don't actually know what inductive resonance is, but assume it is something to do with the excitement of one part of the chlorophyll molecule starting a chain of excitement? If that is what it means, then I don't think this happens. Following ejection of electrons from the chlorophyll molecule, these are quickly accepted by other electron acceptors and subsequently passed out of the vicinity of the chlorophyll (otherwise they would fall back to their original state within the chlorophyll molecule).
As for whether they are efficient - I couldn't say as my course doesn't cover much of photosynthesis (much to my annoyance since it is probably the most complex and important biochemical pathway in existence!), but I know that artifical photosynthesis (i.e. acellulare - in a test tube) would be extremely difficult (if not impossible at the present), as it is obviously far more complicated than just exciting a few electrons. However, if we were looking for efficiency, I would imagine photosynthetic bacteria to be far more versatile than plants in the absorption spectrum of their chlorophylls.