Both the Sonata and the Accord have considerably less trunk space than the Taurus. The Taurus and Crown Vic are both listed at 21 cubic feet. The Sonata comes in at 16 and the Accord at 14. Further hurting the Sonata and Accord is the fact that both of them use gooseneck trunk hinges, whereas the Taurus uses compact ones with gas struts that don’t intrude into the trunk (like the 2010 Sonata used).
Ford also brags that the 2008+ Taurus holds eight golf bags. Great, but it only seats 5. :S
For pure trunk space, the Taurus and CV are the clear winners - but how well a wheelchair fits may vary even with the same volume in the trunk.