Bear in mind that a superserver of any sort is only necessary if you configure mg-dbx-napi to connect to IRIS over the network.  The best performance is realized by connecting to a local IRIS instance via its API.

That said, the reason why we developed our own superserver is because, as far as I know, the IRIS superserver does not have a public interface.  In other words, it only works for InterSystems products.  If this situation ever changed, we would of course converge on the superserver embedded in IRIS.  This would make our installation process much simpler.

I've come to this party quite late but there is yet another solution to consider ...

https://github.com/chrisemunt/mg_php

This solution provides granular access to Cache/IRIS globals, functions and classes.  It is network based and can therefore be used in enterprises where the web server and PHP engine are installed on a separate server to that hosting Cache/IRIS.

An earlier version of this module has been running in the field for quite a long time but it has taken me a while to get around to making it more widely available.  In fact, those who have a penchant for a certain line of fast food might have used this code already :)...