If memory serves, I saw the remake in a theater and the original on TV, so it's a bit of apples and oranges. I do remember a supreme monent in the Nyby / Hawks version, in which the scientists open the door to their domicile and are faced with the Thing--great timing, but a moment that's been used often since then. Overall, the remake for me is more gripping.

I haven't read the source material, but I'll accept the assertion that the Carpenter version is more faithful (not that this counts for much in all cases). In general though, the notion / metaphor of a shape shifter (ignored by Lederer / Nby / Hawks) is particularly appropriate for a visual medium like film, and this may account for the greater thrills of the remake.