Wrong question. Start with what your goals and objectives first. Then figure out what to do from a tax perspective. As for AB trusts, there are lots of trusts. A is usually referred to as a marital trust and B the by pass or exclusion trust. You might not need or want any trusts. You can leave the exclusion amount to kids and the rest outright to your wife. But is that what you want? If your wife remarries following your death all assets bequethed to her (whether under your will or by title as discussed below) could be then bequethed or given by her to her new boyfriend. Not a pleasant thought. A trust can prevent this. If your wife is say a physician and concerned about malpractice, you'd want a trust to protect her. Trusts are often the best approach (regardless of the estate tax).

By the way, joint assets pass to the survivor on death. An IRA passes to the beneficiary. You may have few assets or no assets to pass to the B or by pass trust. Whatever decision you make you have to coordinate the planning in your documents with the title to your assets.

Depending on the state you live in if you fund a by pass ("B", credit shelter, or exclusion or family) trust with the maximum $1.5M (2005) federal exemption amount you may trigger a state level estate tax. Think hard before doing this.

If your estate is $1.7M get an estate planning specialist. There can be a myriad of other issues. Its not only about estate taxes. There are potentially asset protection, control, income tax and other issues, all of which you want addressed right.