Agile technology curves provide a possibility as well to compare the performance of several technologies. The typical question is usually at SharePoint and BPM or workflow topics is to use K2 or Nintex. Let we consider in the following simple SharePoint on premise installations.
Set up time and cost (before Q1): As Nintex can be very fast, typically in hours, installed on a SharePoint environment. Getting K2 installed is much more complicated. The similar is true for licensing as well. Although the two frameworks have got different licensing model, in simple farm scenarios, like having one or two front end servers, Nintex is usually cheaper.
Effective agile development (between Q1 and Q2): One can implement very fast small workflows with Nintex; the technology is pretty much user friendly and can be used by advanced information users. However, as soon as the workflows getting complicated or a lot of external systems have to be integrated the technological limit is reached pretty fast. On the contrary you can do with K2 a lot, implementing complex workflows through several farms or external systems. However you really need the competence for implementing such a workflows. In this sense the Agile period of K2 is much longer, but I would estimate that delivering a use case costs more than with Nintex (not necessarily in time but as a development cost due to the special knowledge).
Architecture limit (after Q2): As soon as you reach the architecture limit it gets ugly for both frameworks. You need very special development knowledge and some scenarios can be developed from the manufactures itself. Certainly the limit is pretty much different for the two technologies, as you will have difficulties if your workflow wants store information in an Oracle Database, it is not a big problem for K2.
Figure 1. agile technology curve comparision between K2 and Nintex