A well-written will allows your estate to be distributed legally and efficiently, costing your beneficiaries the least money and heartache. But you don't need an attorney to write a will. A number of software providers promise to help you draft a legal will for far less than you'd pay a lawyer.

Like tax software, these products guide you through an interview to draw out your intentions regarding, say, how you want your property distributed and who you want as executor of your estate.

We tested three electronic offerings: LegalZoom, Rocket Lawyer, and Quicken WillMaker Plus. The first two allow you to create a will online; the third is available as either a download or a CD-ROM (see Product details). First we created profiles of individuals from three different New York families. Our reporter then completed the interviews as if she were those individuals, drafting nine wills in all.

We sent the wills and interview records—with product identification hidden—to Gerry W. Beyer, a professor at the Texas Tech University School of Law in Lubbock who specializes in estates and trusts. Beyer judged each product on how comprehensive the interviews were and how much information was provided, and on the overall quality of the wills. Our reporter evaluated the software for ease of use. See How 3 products handled 3 scenarios. for more details on the scenarios and how the products worked.

All three are better than nothing if you have no will. But unless your needs are very simple—say, you want to leave everything to your spouse with no other provisions—none of them is likely to meet your needs. And we found problems with all three:

Outdated information

We tested the products in mid-March, and two referred to federal estate-tax limits that were outdated as of Jan. 1.

Insufficient customization

The products rarely referred in detail to state estate law. So they offered no guidance on how states treat wills that, for instance, fail to leave property to children born after a will is signed. (WillMaker Plus doesn't do Louisiana wills because of the state's unique estate laws; Rocket Lawyer provides a Louisiana will but recommends that consumers consult a lawyer.)

Too little flexibility

We found it hard to distribute property the way we wanted to. WillMaker Plus, for instance, provided arbitrary age and time limits for some provisions. The program wouldn't let a child's trust go beyond age 35 or set up conditions on bequests in a will, such as stipulating that a child receive money only after finishing college.

Too much flexibility

After you finish the Rocket Lawyer interview, the program allows you to edit your completed will. LegalZoom lets you put anything you like in the special-directives section. Both features could lead you to add clauses that contradict other parts of your will.

Incompleteness

None of the packages created a special-needs trust. Only WillMaker Plus gave information on registered domestic partnerships and included a pet trust in its main interview. None of them touched on "digital assets," such as ownership and management of server-stored documents and photos. And none dealt with specifics on compensating executors. (LegalZoom sells a stand-alone pet-protection agreement. Rocket Lawyer says it's adding pet and digital-assets options this summer. And WillMaker Plus 2012 will address digital assets.)