I don't hold stock of Chauvet, but I am a distributor, so the Abyss wouldn't be a problem. If it's subtle mood lighting that you are after, then consider the Abyss, Retrobeam (Oil wheel projector), or a colourchanger.
The original NJD Chaos was 100W, so a little underpowered by todays standards, and if you have 250W + effects, or you do large venues then it is likely to look lost. The New Chaos 2, is better because they have up rated it to 250W, but slightly bigger / heavier as a result.
The Datamoon has been around for many years, and is an excellent effect, and during the latter part of the 90's it won awards. All 250W effects are very similar with regard to size / weight, since they all use a similar rated transformer to lower the voltage to the 24v that the lamp requires and this accounts for the weight.
The Vista / Datamoon are similar effects, and now even made in the same factory!, although there is a vast difference in price

. The Vista also has 15 gobos / colours as opposed the the Datamoon which only has 7. Both can be controlled by DMX - Both can be linked together!.
A lot of the decision comes down to personal choice, and with that I can't really help you