Should I Dither ?

Okay, let's do Dithering again - we haven't done it for ages! Whether it's worth dithering depends entirely upon where the noise floor is. Unless you've taken steps to reduce it (NR for instance) it's going to be way above the -90dB point where it becomes worth it - vinyl's just not that good! But generally with a conversion to 16-bit you'd do it, but not because of the noise floor of the tracks themselves. You'd do it because if you put a fade to zero on the end of a track, all of a sudden you're at the point where you run out of bits. And the background falls off a cliff in one jump - sometimes audible, especially if it was a quiet track. What the dither does at this point is effectively to lower the noise floor by quite a bit (the explanation is complicated, and a very clever application of statistics) but it puts the lowest cut-off point well below the threshold of hearing - assuming that you are listening to the track at a sensible level. The pont of all of this explanation is that because these artifacts are at such a low level, it hardly matters which dither you use, because you could only detect what was happening right at the end of your fade. Adaptive dither takes way longer to calculate because it has to analyse all of the audio in your track, and the shaped dither artificially moves the dither noise so that in theory it's less audible. Personally I think that it doesn't matter whether it's triangular or not - mine's set to Gaussian (shaped) and that's fine.

The most important thing to note about dithering is that you should be careful not to do it twice. That's an easy trap to fall into, and the best way to avoid it is to make sure that after you've used it, you reset it to Off. If you are going to use another app - like Ozone, for instance - to do your dithering then there's a slightly different procedure to go through which involves doing your 16-bit dither to the 24-bit track, and then leaving the dither in Audition off when you do the save (otherwise you do it twice). It all works fine, but it's a bit of a faff, quite frankly, for a 'benefit' that you almost certainly won't hear.