A parent recently told me that the school district preferred a 504 plan over an IEP for her child with special needs. The parent asked me whether an IEP is better than a 504 plan. I said that, all else being equal, an IEP is better.
The Individuals with Disabilities Education Act, which mandates creation of IEPs, is filled with procedural rights for parents. The Rehabilitation Act of 1973, which includes section 504, has far fewer procedural rights. For example, the school district must hold an IEP meeting every year and write a new IEP document - in practice, drawing on the previous IEP. By contrast, a school district is not even obligated to create a 504 plan, so long as the student is able to participate as if the student was not disabled. When a 504 plan is created, the district has no obligation to periodically review the document. This means that the district could go a long time before stopping to ask the parents about their views on the accommodations at the school. And even if your child has an IEP, the requirements of Section 504 still apply.
In practice, some districts are willing to offer more in a 504 plan than in an IEP, which can be a good reason to accept one rather than push for an IEP. But if your child has a medical problem that interferes with learning, including learning social skills or life skills, then the district basically has no legal way to deny your child an IEP.