I'm setting up Google Analytics and KISSmetrics for around ten different services (different websites/apps with different domains), all of which share the same login/signup service. I want to be able to track our users coming from one service, going through the login/signup service, and then going back to the service they came from.
My current setup is that I have only two properties, one for staging and one for production. I fire the appropriate property using Google Tag Manager. I then filter the properties into different views based on which services the user came from.
I have never worked with Google Analytics or KISSmetrics before, but I have read about the pros/cons about using a single property and filtering, vs using separate properties. I haven't really found anyone who was in my exact situation though. I would love some advice from someone who's worked extensively with either or both services.
Using the same property for many domains brings problems big and small. There are a lot of settings at the property level. If you use one property for ten domains you will have 2 custom dimensions and metrics per domain instead of 20; you will have to be very careful if you use the data upload lest data shows up in the wrong view; you will not be able to link your webmaster tools accounts since this happens at property level. There are probably other caveats.
I would suggest a two pronged approach: first use a property per domain/service to collect data per domain to have use of all property settings. Then use another property to collect data across all services (needs to be setup for cross domain tracking); since they use the same login id you should be able to generate a user id from the login data and enable session stitching, so you can even track them across devices (you need to create a dedicated user id view for that to work).
I have nothing useful to say about Kissmetrics.