There are plenty of reasons one may prefer Django's ORM over SQLAlchemy. For example, SQLAlchemy doesn't have robust support for the most popular spatial database implementations: PostGIS, MySQL, Oracle, and SpatiaLite. Django's ORM does.
Moreover, it did not take four years to develop multi-db support. This was a GSoC 2009 project that was merged in 2009.
Moreover, it did not take four years to develop multi-db support. This was a GSoC 2009 project that was merged in 2009.