Both of the systems are crap, when we were evaluating them for nationwide purchase we chose TETRA because of systemic safety features (like local DMO handover modes for public safety use in noisy environments), but when I read their crypto choices I made screwy faces constantly, I wasn't in the slightest bit surprised when this research came out.
I remember at the time some ex signals military folks trying to tell me that the encryption barely matters as the channel selection rate is so high you'd need multi-site intercepts to even make heads of tails of it, sadly they didn't really seem to understand how far SDR and compute has come. The whole experience to this day flavors a lot how I think about military and telco thinking around the whole space, everything touching that boundary feels infected with oldthink.