I will answer from experience:
Q: The second does the opposite. Which is the best practice for the "C" in backbones spin on MVC?
A: There is no Controller in current Backbone http://backbonejs.org/ - "C" happens either in View (most cases) or in Router (see below).
Q: The first tut defines urls in the Model, whereas the second defines it in the Collection. Which is the better practice?
A: There are cases when you don't need collections. In case when you don't, your model absolutely needs a URL. When you do have a collection, URL you specify for Collection will apply to its models.
Q: The second tut makes use of Backbone.Router, while the first one does not. Which is best practice?
A: Rule of thumb - you want to use Router in 2 cases: 1) when you want to have history, and 2) when you want to have permalinks. Otherwise you don't really need router.
