Okay.
I said they would be more beneficial than RRSPs.
In the case of RRSPs, contributions are deductible. In addition, contributions and investment income are not taxed at the time, but are taxed during retirement. They are also included in the income used to calculate income-tested benefits such as the GIS.
In the case of TFSAs, the opposite is true. The reason they are more appealing to low-income individuals is that neither the investment income earned in a TFSA nor withdrawals from it are included in the calculation of income-tested benefits.