Is any one of the three less important to you?
Soil is important; otherwise, would such greats as Prairie Dunes, Garden City GC and Walton Heath even exist?
Topography is important; look at Shinnecock and Royal Melbourne West where one nine on each courses seems better than the other, all thanks to topography.
Setting is important as anyone who has played Stanley Thompson's Banff, Jasper, Cape Breton and Capilano will testify. Without setting, would Bandon, Oregon be the hottest new destination in golf?
Relative to one another, which is more important to you between soil, topography and setting? Of course, a Cypress Point which has all three in spades is wonderful but alas, such a site is the exception rather than the rule.
My own answer has significantly changed over the past five years. Initially, topography ruled with Yale being close to the ideal but in the past few years (as The Carthage Club profile indicates), I now place more importance on soil, as it is at the heart of how the game can be played - sandy loam promotes fast/firm conditions, thus opening all design options to the architect.
(On a side note, when I moved back to the U.S. in 2000 and before the great tiolet flush of wealth, several guys in Charlotte were primed for The Carthage Club - provided it was located somewhere near Charlotte. The fact that the sand was located 1 1/2 hours east in - ironically
- the sand hills of North Carolina was inconsequential.)
Cheers,