Apparently, the GCAT site at Bioplanet hosts such a comparison open to everyone. By going through the charts, I do not see any qualitative difference between the two programs. In other words, if someone removed the program names from the website and asked me to find GATK from the comparative charts, I could not have done so.
Here is one of the comparative charts among many in their site -
Given that BALSA runs way faster, produces results as good as GATK and comes at no cost, it is unclear to me why people would pay so much for GATK. One quoted number I saw in twitter was ~$40K/license (!!!), although the others said the actual price is ‘not that high’.