[obviouslygreen]

It is good advice; it just isn't time-effective to do a thorough job. By the time you've gotten through the tutorials and maybe built a couple simple sites, you've probably gotten to the beginning of understanding how it works, but you have yet to do basically anything that would be considered working with the framework as it applies to what you'd actually do on a real project. You might understand the very basics, but extrapolating that into "this is how working with it actually is" carries the very real possibility of a rude awakening.

[rhizome]

How thorough does an evaluation need to be? I'd suggest that doing a few things less-thorough than a real project is sufficient to get a feeling for the framework. There are real projects done in both frameworks, there isn't going to be a point where you find some pitfall and go, "welp, looks like we have to start over in Rails" or whatever.