For completeness, I’d like to add that the license should also be a criterion. I think librsvg is GPL+LGPL, resvg is MPL, and the Adobe SVG Native viewer is Apache 2.
But after the Macromedia acquisition in 2006, Adobe dropped their interest in SVG and concentrated on Flash. Apple’s resistance to put Flash into iOS gradually devalued the Adobe Flash platform, and now we’re seeing Adobe (along with others) pick up their work on SVG after a 10+-year hiatus.
I wouldn’t be surprised if the newly-opensourced Adobe SVG Native viewer was a spin-off of the Adobe SVG Viewer from 20 years ago.
It seems to me that the recent Adobe opensourcing of the Adobe SVG Native viewer (which is C++ 11) and their work on the SVG Native spec shows serious commitment on Adobe’s side. It's hard to predict, but I suspect that this project will be well-maintained and will become the institutional support from possibly also other players.
It wouldn’t be a great surprise to me if, say, someone like Qt would at some point integrate the Adobe code into the Qt framework and replace their old SVG Tiny implementation.
I also know that resvg (which is written in Rust) is rather active, but it seems that it's an individual development.
Best,
Adam