As I grow older I guess I am growing more fond of statically typed languages. It's easier for my decaying/distracted brain to reason about. There is less mental overhead I suppose [might be a good blog post?]
They both have a good database migration system and various generators for scaffolding views, controllers, etc. To be fair I believe Entity Framework does most of the work for the .NET side on the database developer tooling but I just consider it part of the .NET ecosystem since it seems to be the go-to ORM/database tooling library. I want to be fair to Rails -- I really think they set the bar very high for other frameworks. Productivity w/ Rails was unprecedented when it first came out. I started during the Rails 3 to 4 upgrade.
Both ecosystems have easy access to outside libraries using Nuget/Gemfile. So pulling in a background processor like Sidekiq [Ruby] or Hangfire [C#] is fairly easy.
Cross platform support is acceptable across both frameworks as well. I can setup an EC2 instance and run both Rails and .NET applications side-by-side. So deployments are going to be similar but I would argue that .NET has the upper-hand because it can deploy do a self-contained deploy so you don't have to worry about installing dotnet in the deployment environment.
I am using Blazor Server and I am not going to say something drastic like it will kill React but it is pretty awesome. I can build my entire web experience with C# but with Rails I have to introduce React when I sometimes dont want to. Blazor prevents me from having to write HTTP code from my front to backend systems and as an indie developer that is a godsend.
Both have gorgeous documentation -- I thought Rails was good and thorough but .NET ate their lunch.