Thermal compound matters very little, maybe 1-2C. The NT-H1 that comes with the Noctua is a very good thermal compound though. I would get the D14, the Zalman looks cool and all, but the Noctua has been tested and is one of the best air coolers around, it's pretty quiet as well.
But, the Zalman looks hella sick and is triple fan, so it is probably very good as well. Pick the one that appeals to you more, both will do the job well.
If it were a matter of looks I'd jump on the Zalman in a second. It looks so much nicer than the beige fans on the DH1. Unfortunately my case has a pretty opaque window (it's a heavy black mesh grill) So I won't be able to see too much. Top that off with the fact that it's likely to be kept on the floor and well, sadly looks just fall off the chart.
I'm much more concerned with performance, stability and longevity. I've heard that both of these coolers can place some significant strain on the mobo. Is that something to *really* be concerned with, or is that something that only bites you with really budget motherboards in really budget cases?