Jerusalem — Musing on the split between Palestinian leader Yasser Arafat and some of his men backed by Syria, Egypt's President Hosni Mubarak said gloomily, ''No one but Israel will benefit from this.''
Whether or not Israel is the sole beneficiary of the Palestine Liberation Organization chief's troubles, Israeli officials definitely view them as a bonus for their country. ''It is good for Israel,'' said Foreign Minister Yitzhak Shamir, ''that there are domestic quarrels, breakups, and divisions within the organization of the PLO.''
But Israeli experts on the PLO question whether the defeat of the pragmatic Mr. Arafat by more militant PLO hard-liners, or a compromise that enhances Syrian and Soviet influence over the PLO, will benefit Israel in the long run.
For the Israelis the vicious infighting within the PLO is a godsend. The government is under mounting domestic pressure to bring vulnerable Israeli troops home from Lebanon. But the Israelis refuse to pull back all their men until the Syrians and the PLO - who have rejected the Israel-Lebanon agreement detailing Israeli pullback terms - withdraw their Lebanon-based troops.
The highly publicized disintegration of the PLO has given the Israeli government valuable ammunition to use against antiwar critics by arguing that the war in Lebanon achieved a key aim: the physical destruction of the PLO.
''It (the PLO's split) is the result of demoralization and disappointment in the wake of the tremendous defeat they had in Lebanon,'' Mr. Shamir said.
The possibility that the PLO might veer onto a more radical tack, abandoning Arafat's exploration of possible diplomatic avenues to a solution, does not worry the government. Prime Minister Menachem Begin has said repeatedly that Israel would not negotiate with the PLO even if the Palestinian organization recognized the Jewish state, since the Israelis believe such a move would only be a trick.
Should the PLO become more radical, Israel's total rejection of the organization would become that much easier to explain to European nations and some circles in the United States sympathetic to Arafat's appearance of moderation.
Shamir noted frankly, ''I am not afraid of the radical-ization of the entire organization (the PLO). Practically speaking it may be that Ara-fat's tactics are sometimes more dangerous for us.''
But some Israeli experts on the PLO doubt that its travails will help Israel. Prof. Yehoshafat Harkabi of Hebrew University, former head of Israeli military intelligence, told Israel Radio, ''It is often assumed that any infighting among the Arabs is automatically good for us. However, groups within the PLO may increase their terrorist acts against us as a way of gaining points in the internal power struggle. Also, if the organization ends up taking a harder line as a result of the internal struggle, the possibility of a political solution may be diminished.''
Dr. Matti Steinberg, a research fellow at Hebrew University's Truman Institute and a leading expert here on the PLO, says the split within PLO ranks and between Arafat and Syria will ultimately be papered over to the benefit of Soviet influence in the region. Dr. Steinberg does not foresee a wholesale PLO switch from diplomatic moves to terror tactics.
''I think Arafat will try now to solve his internal problems by aligning himself closer to the Soviet position,'' Dr. Steinberg said in an interview. ''He will ask the Soviets to try to persuade the Syrians to lighten their pressure on him.''
The price? Dr. Steinberg believes Arafat will abandon his previous interests in the now-moribund Reagan Mideast peace plan, which suggested that Jordan and non-PLO Palestinians negotiate with Israel over the return of the Israeli-occupied West Bank and Gaza.
Instead, he believes the PLO leader will back a regional negotiating process involving the Soviet Union, a position moderate Arab states may also adopt. This formula is supported by Syria and by more radical marxist PLO leaders like George Habbash and Naif Hawatmeh, who are now mediating between Arafat and Syrian President Hafez Assad. ''But this will lead to a cul-de-sac because both Israel and the US oppose Soviet involvement,'' adds Dr. Steinberg.
Dr. Steinberg feels Jordan or West Bank Palestinians will not join negotiations without the PLO.
James Dorsey writes from Cairo that sources in the Egyptian capital feel the PLO chairman may emerge from the internal strife within the PLO and the rupture in relations with Syria as a more independent Palestinian leader.
Aides to Arafat say he may soon resume his dialogue with King Hussein of Jordan. Talks between King Hussein and Arafat earlier this year aimed at working out a formula for the implementation of President Reagan's call for Palestinian self-rule in association with Jordan collapsed as a result of Syrian and radical Palestinian opposition.
Arafat's political future is believed to hinge on the attitudes of the Soviet Union and two radical Palestinian factions headed by Mr. Habbash and Mr. Hawatmeh toward both Syria and the dissidents within the PLO.
Arafat's expulsion from Syria puts the Soviet Union with its close contacts to both Assad and the Palestinians in a difficult position, sources said.