NEW YORK (CNN/Money) – The tax panels of the House and Senate each passed tax bills Tuesday evening that differ in two key ways: Only the House version calls for an extension of the reduced rates on capital gains and dividends; while only the Senate version calls for major AMT relief in 2006.

After postponing its vote three times in less than a week, the Senate Finance Committee finally passed a revised tax bill that omitted a provision that would extend reduced investment tax rates.

Sen. Charles Grassley (R-Iowa), chairman of the committee, had included a one-year extension in his original proposal but dropped it when it became clear the bill would be defeated by the stiff resistance to the provision from all the Democrats on the committee, as well as one Republican – Sen. Olympia Snowe of Maine – whose vote was needed to pass the bill. The Committee has 11 Republicans and nine Democrats.

The provision called for capital gains and dividends to continue to be taxed through 2009 at 15 percent (5 percent for low and middle-income taxpayers, reduced to 0 percent in 2008). Those rates are currently set to increase after 2008.

Opponents of the measure say it's hard to justify an extension of a tax break that disproportionately benefits higher income taxpayers when lawmakers, under pressure to reduce the deficit, are also proposing to cut spending on programs like Medicaid and food stamps, which affect the poor and working poor.

Proponents, meanwhile, say the tax cut extension is desirable sooner rather than later because delay might create uncertainty in capital markets. And, in general, they say the reduced investment tax rates have boosted stocks and the economy.

The Senate Finance Committee's tax bill was passed by a vote of 14 to 6, said committee spokeswoman Jill Gerber. Snowe voted in favor of it as did three Democrats on the committee -- Sen. Max Baucus (D-Montana), the committee's ranking Democrat, Sen. Blanche Lincoln (D-Arkansas) and Sen. Charles Schumer (D-NY).

The absence of the investment-tax-rate extension in the Senate bill doesn't mean the prospects for an extension are dead.

The House Ways and Means Committee passed its own amended tax bill Tuesday evening, which includes an extension of the reduced capital gains and dividend tax rates for two years through 2010.

Publicly, Republican members of the Senate Finance Committee who have been pushing for the extension say they'll get it one way or another.

Quoted in various reports, including Tax Notes, a publication of publisher Tax Analysts, Grassley said last week, "If we pass a tax bill, it's going to have extension of capital gains in it, or we won't have a tax bill. And whether we have one in the Senate or not, the House is going to have one, so it's going to be conferenceable. We'll end up with it."

Both the Senate's and House's amended tax reconciliation bills include a number of other tax breaks likely to garner bipartisan support – for example, extensions on the tuition deduction, the saver's credit, and the option to deduct state and local sales tax paid in place of deducting state and local income tax. The Senate version also includes various tax breaks for survivors of hurricanes Katrina, Rita and Wilma.

And, unlike the House Ways and Means Committee bill, it calls for a one-year increase in the income exemption levels of the Alternative Minimum Tax (AMT). The "patch," as it's known, would prevent an additional 17 million taxpayers from getting hit with the tax originally intended to ensure the very wealthy don't dodge the tax bullet.

Committee chairman Bill Thomas (R-Calif.) had said in various reports last week that not including a patch on AMT exemption levels could spur momentum for tax reform by revealing the full impact of the AMT. His tune was a bit different Tuesday. "The chair ,,, felt that we probably shouldn't benefit the wealthiest of the wealthy, which clearly are those subject to the alternative minimum tax," Thomas was quoted as saying in an article in Tax Notes Wednesday.

According to estimates from the Urban-Brookings Tax Policy Center, absent a patch, the number of married couples with two kids and an adjusted gross income between $75,000 and $100,000 who will be subject to AMT will jump from 1.8 percent this year to 73.4 percent in 2006.

Next the Senate tax panel's bill will be sent to the full Senate for consideration, and likewise the House tax panel's bill will go to the floor of the House. After that, lawmakers from both bodies will convene to negotiate which elements should be included in the final piece of tax legislation that must be voted and approved by both the House and Senate.