Just looked in to RGT - it looks prettier than Zwift! Based on this review video I've just watched, it sounds like there's features in it which will make it more geared towards competitive riders
https://youtu.be/rpU-HjAOZqg?t=292
Sadly if you look at the graphics at 10:12 in that YT video that is the level of the graphics for some of the routes with the occasional section being more populated. Closer up with a screen in front of you you will see the lower textures and glitchy terrain modelling. Zwift has been gradually populating whole regions with more lighting and atmospheric affects. At least I can see that with a dedicated GTX 1050 Ti in my HP i5 Deskpro. They just need to add more real routes to be king!
I've been trying every 6 months or so and the interface has vastly improved becoming very close to Zwift with the basic functionality (my NEO worked perfectly apart from lowering the climb setting to 50-60% like in Zwift) but lacking the other rider info. Mainly because there's still very few people on it still. I went from an 1100 people ride round Yorkshire to maybe 20 people on the entire Stelvio climb in RGT.
I will still keep trying but the premium upgrades don't interest me so there's no reason for me to subscribe as Zwift is plenty as it is. I do keep thinking of stopping Zwift during simmer anyway and just re-subscribe for winter training.
<EDIT> I went back to RGT and tried another route today and to be fair the current rides vary in quality and Stelvio isn't the best example. The coast ride I tried was much more detailed just with more simplistic lighting and flat textures. Apart from that it was nice to ride another route rather than repeating Zwift all the time.