Depends on who's reviews you look at as to whether they are comparable or the RTX is a lot better, the RTX is bound to be more expensive as it supports Raytracing which AMD don't at this point. As far as Trainz is concerned I doubt there is a lot of difference.
Personally I don't touch AMD graphics, I stick with what I know works for me which is Nvidia. I do use AMD CPUs though on two of my PCs.
You can see the different take on what is equal to or better than on these links.
I have chopped and changed between ATI/AMD and Nvidia video cards over the years as the value proposition has changed. The prices on Nvidia cards have increased a lot during Coronavirus; the cheapest 2080 Super has gone up by around £100 compared with early March.
Ten years ago I would have agreed that AMD GPU's had their issues particularly with the likes of the Sapphire boards over heating and poor reliability but in recent years I don't think there is a lot to pick between them. Both AMD and Nvidea have good and poor GPU/chipsets as do the leading manufacturers produce good and lets say not so good graphic cards I think you have to judge each on their merits and frames/bucks. I mix makes of CPU and GPU with few issues and those I have are generally of my own making.
What I've never been able to discover in respect of Trainz is whether there is anything to be gained from matching a Nvidia card with a Gsync monitor or a AMD Radeon card with a FreeSync monitor perhaps others have such a setup and could advise. Peter