Why do some conifers lose their leaves in winter?

Walking through the park today, we noticed a conifer tree that had either shed its leaves or was just plain dead. We then remembered that tamarack and larch trees are some of the very few coniferous trees that are not also evergreens. So, of course, the obvious questions occur, lIke "how?" and "why?", requiring recourse to the interwebs (yes, that old thing is still around!)
So, first things first. Wide-leafed deciduous trees lose their lives in winter to save energy and conserve water. Their large leaves can soak up so much sunshine and produce so much carbon dioxide during the summer growing season that they can survive the winter without producing more, so they jettison their energy-hungry leaves and live off their fat, so to speak. They basically go dormant for a while, similar to a state of hibernation.
Needle-bearing conifers, on the other hand, don't produce as much CO2 during the summer, but their requirements are much lower, and a waxy coating on the needles reduces water loss and snow accumulation in winter.
So, it's a case of horses for courses - two very different strategies achieving the same ultimate end: survival. The broad leaves of decidious trees live fast and die young; the needles of conifers are more energy-efficient and stay the course. (Incidentally, it is a fallacy that conifers lose all their needles over the period of a year - in fact, individual needles may live as long as 20 years before turning colour and falling off).
What then of tamaracks and their cousins, the larches? Why do they buck the trend and lose their needles each winter?
I've still not found a very satisfying answer but, from what I can gather, tamarack needles are sparser than most conifer needles and so can receive more sunlight, as they shade each other less than either other conifers or broad-leaf trees, and thereby accumulate more CO2 during the summer. Also, they have chosen not to produce such waxy needles, which requires less energy. And finally, they use nitrogen more efficiently than other trees, and are able to recycle and reabsorb more nitrogen than any other tree before they lose their leaves in the fall.
So, there you have it: not totally satisfactory perhaps, but at least an explanation of sorts.