Some day in June, a small group of House and Senate Budget committee members will sit down and decide what the federal budget ought to look like for the next five years. The outcome of that conference on the budget may well determine the course of this nation's economy for the rest of this century.

There are surface similarities between the House and Senate budgets, but they mask fundamental differences that will have an impact on our nation's future.

First, the House budget recommends a defense spending level that its own Armed Services Committee overwhelmingly rejected earlier this year. Indeed, that committee, the Senate Armed Services Committee and the full Senate have all agreed on no real growth in the first year and 3 percent real growth in 1987 and 1988 for defense spending. The House budget would cut $32 billion below that level during the three years.

It seems altogether improbable that Congress will ultimately approve such an extraordinary cut in defense spending for many reasons -- program efficiency, national security, our commitment to our NATO and other allies, the continued defense buildup of Soviet forces, among others.

Second, the House budget leaves about 30 percent of the federal budget "off the table."

You'll recall the hailstorm of media and partisan criticism that pummeled the president's February budget. After all, the criticism ran, he left about half the budget "off the table."

To his credit, the president has now put all of federal spending on the table. The Senate has done the same thing. It is the House that's running away from any changes, however temporary or small, in the multibillion-dollar pension plans administered by the federal government.

In short, by not sking for shared sacrifice from pension recipients, either by a COLA freeze for a year or by pension reforms, the House budget shies away from the fundamental reform that a prosperous future demands.

Third, the House budget, like the Senate budget plan, freezes most of the domestic accounts in the federal portfolio of programs. But, while the Senate kills 13 domestic programs outright and radically reduces many others, the House would kill only general revenue sharing and lightly touch a few more programs with 10 percent reductions in the first year only. No other long-term reform, no other termination, no other fundamental restructuring of program exists in the House budget. Without such a fundamental restructuring, without reducing significantly this nation's commitment to future spending, the $200 billion-plus deficit now afflicting our economy will continue.

Finally, the House budget recommendation fails to provide any mechanism that will take its saving assumptions beyond the realm of hope to the realm of reality. While the Senate boldly imposed "reconciliation," or mandatory instruction to save, on its committees for almost every penny we wanted to cut from the deficit, the House backed away from such a broad step. In the first year alone, for example, the House reconciles only $11 billion of savings, compared to $29 billion in Senate reconciliation. Over three years, the House reconciled $37 billion, the Senate $135 billion.

And while the savings from the appropriations process are not subject to reconciliation under the budget act, the Senate did adopt separate "caps" on the overall level of defense and nondefense appropriations.

Thus, the House's hopes for out-year savings are by and large fond desires: the Senate at least imposed a certain probability on the likelihood of out-year cuts by providing a mechanism to enforce its savings assumptions.

It is critical to remember, however, that even if the House Budget Committee's recommendation were to be implemented in its entirety, it would cut deficits during the next three years by $259 billion, while the Senate budget would be nearer $300 billion in cuts.

And over five years, the Senate-passed budget plan would get the nation within $20 billion of a balanced budget, while the pending House budget might leave us nearer a $75 billion deficit.

In short, the House is faced with a budget on the floor that has an unrealistically low defense number, that shies away from changing COLAS, that fails to undertake fundamental pension and other domestic program reforms, and that provides faulty enforcement provisions.