With deference to Herb, I am not sure the gloss is, in fact, thicker. Someone got a spec or factory word on this? From what I figure (a reasoned guess, admittedly), the satin is identical in every respect to the gloss with the simple deletion of the the labor involved with buffing to a gloss. Simple: it's a cost cutter. Further, I have never heard nor read anywhere that it is more thinly-applied than the gloss finish.
What I do recall reading long ago, though, is that since Taylor brought in the "robo-sprayer" Bob mentioned the finish got thinner (arguably better for tone since there is less "stuff" to hamper the soundboard's movement), was more evenly applied, and resulted in far less airborn loss/waste. I can't recall when robo-sprayer came in but my failing memory says somewhere around 2000(?).
Frankly, I wouldn't waste a moment's thought on which is better in terms of thickness/durability ...for taylor's guitars, that is. It's a simple preference, really. While gloss represents a more "finished" guitar to the marketplace, there are those who say they like the satin. As for which will "hold up" better, I'd say it's irrelevant for all practical purposes of normal use/wear.
Edward
