
All three software packages offer an interview based approach to doing your taxes in which the software interviews you about your life situation and fills in the forms for you (this is the default approach for all three packages).
TurboTax
TurboTax begins with some basic questions about you, your family, and facts about your home, job and investments, and whether you are supporting someone in college or have rental income. In a sign of the time, the interview asks right up front if you lost your home through foreclosure.
The interview process then proceeds based on your responses. Once you’ve entered basic wage data and answered income questions, you can choose from among available topics or have the interview ask about every possible type of income.
During the interview process, TurboTax is very tolerant in terms of allowing you to enter partial information. You can mark entries as estimates and add itemized details as well.
TurboTax of course supports import from Quicken, QuickBooks and previous year TurboTax returns and TXF file format.

TaxCut
TaxCut gives you a choice up front as to whether you want to be asked about life changes such as changes to your family or job (no home foreclosure though). If you check this box, it will be sure to include these in the interview that follows. After collecting the usual personal information the program allows you to go step by step or to quickly navigate to any topic. As with TurboTax, the software allows you to enter partial information, mark entries as estimates and add itemized details.
TaxCut can import data from your previous year TaxCut or TurboTax return, and financial information from Microsoft Money or Quicken.

TaxAct
Once TaxAct collects your personal information, it does not divide the interview questions by income, adjustments and credits as do the other two programs. Instead, it allows you to navigate quickly to life events or Q&A through menu entries. By default the interview shows you the form you are filling in. As with the other two programs, you do not need to complete a question in order to navigate through the interview topics. You can also mark entries as estimates and add itemized details.
TaxAct can import data from previous year TaxAct returns.

All of the programs do a thorough interviewing job when it comes to income, deductions and adjustments, TurboTax and TaxAct in particular do a better job than TaxCut at addressing and guiding you through the consequences of life events.
TurboTax vs. TaxCut vs. TaxAct reviewed: