Well, I got BRVR set up and working with only a medium amount of swearing which is good going for me.
Yesterday I did a test ride to a place called Modane in France. This morning, for the main event, I rode up Ventoux from Bédoin.
I'm very impressed. The software itself is a bit on the fiddly side, but once you get going it's superb. If I compare it with the Tacx videos I'd score them equal. They are both great. Yes there are differences, but basically they both provide really good quality videos, with an interesting dashboard of info. Neither exceeds the other at that main task.
Maybe BRVR's screen layout is a bit more pleasing and the recorded tcx files are smoother. Maybe the Tacx software a bit less swearing-inducing in use and set-up. But really these are minor details. They both do a fantastic job at putting pretty pictures on screen to distract me from the fact that I'm just sitting on my bike on a trainer in the kitchen.
I'll be sticking with my existing Tacx subscription because BRVR doesn't have anything to tempt me away and I don't think I want to pay for two subscriptions for essentially the same thing. But if I wasn't already subscribed to Tacx I'd have a difficult choice. I don't know how good BRVR is at doing structured workouts like FTP based intervals. Also I don't know if BRVR allows you to ride your own GPX files, which is a Tacx feature I really like.
Edit: Another - rather unfair- comparison is RGT. RGT is a game simulation with other riders in the simulation, so more of a Zwift competitor. The graphics, while good for what they are, don't give you the sense of place that a video does. On the other hand RGT has other riders, which isn't a feature that I thought would interest me but when I rode Ventoux in RGT I had a Dutch guy behind me, closing in on me all the way until I put my mighty hammer down near the top and left him

That was kind of fun. The procession of fast riders passing me was less interesting. But RGT is quite immersive and another good way of taking your mind off the boredom of turbo training.