To me, SeaORM feels like a well-designed library while many things in Diesel feel like an afterthought or a hack. Which mostly manifests itself when doing something complex and debugging it.
After being frustrated with Diesel, I gave a try to SeaORM and I couldn’t be happier (have been using it for more than a year). It is not perfect but certainly the best ORM I have ever used myself (vs Diesel, ActiveRecord, SQLAlchemy)