ASR920 vs NCS5000

Cisco live on-demand library is a good starting point:
 – just search for “920” and it will return two presentations (although I was expecting more than just 2 presos on these),  there are some comparisons as well as scaling numbers.

Well there are only 3 branches in ASR900 family tree as far as I know,
900 Series (902 & 903),
920 Series,
901 Series,
but yes I guess it’s fair to say they are very different to each other.

Regarding the NCS5k(or QFX counterpart), the same rule apply as always, there’s a reason why these are so darn cheap compared to high-end platforms(like e.g. NCS6k), there are architectural sacrifices that were made during the platform development resulting in numerous limitations and only once all these are understood the device can be considered for a given environment.