I work in an advanced analytics group. We use and have made significant investments in Alteryx. Within that group I am probably the sole user of KNIME. Having spent a bit of time with both platforms I think the first thing you should consider is whether you are going to use the geospatial capabilities in Alteryx and license the data sets (e.g. Experian, Dunn & Bradstreet, CASS, TomTom). If geospatial is important there isn’t a more user friendly option than Alteryx. Creating trade areas with their related demographics is trivial in Alteryx, and I’m not aware of another system that enables that functionality so easily.
If you aren’t going to use the geospatial tools and data I’d suggest KNIME. The integration with R is better and overall it seems to be more flexible than Alteryx