Considering that each time a new resource is available the existing answers should be edited, or a new answer should be added, I would say they are not constructive. That is not for the fact such questions solicit debate, but for the fact they are not a good fit for the Q&A format used from Stack Exchange site.
As with other questions about available resources, the answers tend to just report a link to the resource, or any other data useful to identify the resource (e.g. the title of the course); they don't normally compare a resource with another, to identify the reason why the OP is suggesting a resource, and not another. If they contain that information, then the answers are probably subjective, as there isn't an objective way to quantify what resource is preferable. If who asks the question would make it very specific, then it could be possible to define which resource is better. In that case, it is also probable the question is too specific for help the future readers, which can be said also in the case the answer contains just the data useful for identifying the resource. Future readers would just find references to resources, and they should verify which one better suits their usage.
Another objection to those questions is that, generally, they don't seem to be asked because a real problem. To make a comparison, those questions sound like asking a list of car models because somebody wants to buy a new car.