I like Xamarin but I do not like the dev process yet for the frontend. I think if that would be leaner (more Core2 and potentially command line and reloading instead of recompile: only for dev ofcourse) it would be more popular. Now it is a very heavy process; thats not because of c# or f#; they can both be very dynamic. Not sure why not more work goes into making development smoother.

Having said that, I for one like working with Forms+renderers and a reactive framework a lot more than RN. I can go for years and have my code work fine after updates; I find npm such a nightmare and RN feels too driven (logically) by FB needs.