VS our IAS are techniques..; the safest being always the best, IAS wins... Now, we have other constraints dictated by the less performer. The less performer in this case is a combination of ATC and TCAS.
In order to "smooth" the side-effects of a regulation, the same regulators requested to limit the ROC on the last thousand , and even at 1500 before. Where in IAS mode requires to reduce the power to have this immediate effect, in VS, the thumbwheel makes people feel that they are in control, then they reduce the power in order to maintain the proper L/D, by reducing the speed. With AT, it becomes less a problem at LOW LEVELS, but if going to the first available ceiling, this habit may drive some in the same adventure as this poor Citation.
In my former company we had at least two instances of near stall ( the airplane has hi and lo speed prot, and eventually sorts itself out). but at FL410 when you have " increase speed" , "increase speed" this resumes that the least trusted items on the plane had gone south..
Speeds modes are always the best, just need an open mind to understand them.