ISRAEL'S bargaining power has never been stronger than today - far weightier than before the Gulf war and much improved over 1979, when Menachem Begin signed a peace treaty with Anwar Sadat. The greatest danger now may be subjective - hubris. Overconfidence could lead Israeli leaders to drive too hard a bargain, squandering a major opportunity.The Arab countries encircling Israel continue to possess far greater land mass, population, economic resources, military budget, and armed forces. Taken alone, Egypt, Iraq, and Syria outnumber Israel in each of these dimensions. Together, they far exceed Israel. If we include Jordan and other Arab states such as Saudi Arabia and Libya, the scales tilt overwhelmingly against Israel. Size can be a plus or minus. Egypt's population is more than 10 times Israel's, but Egypt's cultivated and inhabited land is only twice the size of Israel. Arab populations multiply rapidly, producing more mouths to feed, while hundreds of thousands of Soviet settlers are bringing new skills and energies to Israel. Israel has been winning the development race as well as the arms race. At peace with Egypt and bolstered by US aid, Israel has drastically cut government expenditures on defense. Its economy grew at 5 percent in 1990, but with 17 percent inflation. Israel's gross domestic product (GDP) has multiplied by more than three times since 1979, much faster than its neighbors. Israel's GDP is now half that of its neighbors' total output - compared to one-third just a year ago or in 1979. Israel today spends 12 pe rcent of its GDP on defense - twice the US ratio but much less than some neighbors. Egypt has also experienced much economic growth, but its per capita income remains less than one-tenth Israel's. Even oil-rich Iraq never achieved more than $2,000 per capita, and that sum has now plummeted. Iraqi armed forces swelled to 1 million during its 1980-1989 war with Iran and remained at that size when it invaded Kuwait. Since the Gulf war, this number has dropped by two-thirds, but reserves of 100,000 to 600,000 remain - quality variable. Iraq's decline alters many indices in Israel's favor. Iraq, Egypt, Syria, and Jordan now spend only twice what Israel does on defense - not three times, as in 1990. The loss of many Iraqi tanks and planes has reduced the Arab advantage in such weapons relative to Israel from 3:1 in 1990 to about 2.5:1 in 1991. POLITICAL factors have become more favorable to Israel. In 1978, Israel was virtually at war with all its neighbors except Lebanon. Peace with Egypt gave Israel more leeway in dealing with other neighbors. The Gulf war brought changes no less important than Camp David. It split Israel's potential foes - pitting Egypt and Syria with the United States against Iraq, backed by Jordan. More important, the USSR - for decades the most powerful foe of Israel - backed the US coalition. Moscow has now established diplomatic relations with Israel and co-sponsored the Madrid conference. The upshot is that Israel's main foes have been neutralized - Egypt, Iraq, Syria, the USSR, and even the Palestinian Liberation Organization (PLO). Still, Israel must cope with an enemy within and the prospect of mass destruction weapons from without. The Palestinians were the big losers at Camp David. The 1978-1979 accords called for Palestinian autonomy, but left the details unspecified. Global sympathy gave the PLO more clout in the 1980s, which it threw away in the Gulf war. The PLO is represented only indirectly at Madrid. Israel has the upper hand today, but unless it permits self-determination for Palestinians, Jews will some day become a minority in their own land. The Palestinians will not willingly remain in a new Babylonian captivity. How do weapons of mass destruction affect these equations? Iraq's weapons of mass destruction and its capacity to make them have been significantly reduced, but not wiped out. Even conventional warheads could do horrendous damage to Israel's cities. Syria has acquired some 20 Scud missile launchers from North Korea, more accurate than those earlier obtained from the USSR. Syria has negotiated with China for surface-to-surface missiles with a range of 500 kilometers. Syria's Air Force has obtained 70 high-performance Su-22 ground attack aircraft. Saudi Arabia's forces are also expanding and modernizing. Iran seems determined to go nuclear. For now, Israel is still the only Middle Eastern country with nuclear weapons. "The Samson Option" by Seymour Hersch recounts that, in the 1973 Yom Kippur war, Israel threatened the USSR with nuclear-tipped rockets. Since then, Israel's arsenal has enlarged and probably consists of 200 to 300 nuclear warheads. An Israeli threat to pull down the roof is plausible. How long Israel can maintain its present advantages is uncertain. New numbers and imponderables could work against it. Israel can use its present strength to stand defiant or to bargain for a settlement advantageous for all sides.