"He seems like a nice man, a reasonable man, but what difference does one man make?"

Such was the talk in one bar in Moscow after President Reagan's New Year's greeting was beamed over the television at the start of the 9 p.m. news.

Reagan's message was practically drowned out by the music and, except for the bartender, few paid close attention to the unaccustomed guest on the Soviet screen.

Except for those who get their news from western sources, no one in Moscow knew that the American president was going to speak tonight: A government spokesman held a press conference here Friday to announce the mutual exchange of New Year's greetings but Soviet journalists did not attend the briefing and no mention of the event was published in the Soviet press.

And on a day when people were recovering from New Year's Eve festivities, politics was for most a distant subject.

Gathering Soviet reaction to such an event is practically impossible. There is no tradition equivalent to American barroom television viewing and subsequent debate. There are few bars, no public debate, and television is something people generally watch at home.

According to Soviet television, about 100 million watch the main Soviet news program, "Vremya," or "Time." Reagan's message tonight was the first item. Usually, the format is more stilted, with long-winded items on economic progress leading the program and news announcements coming next.

Reagan's address fit into a tradition of greetings read to Soviet television viewers by ambassadors accredited in Moscow on their national days.

But everyone agreed this was different and more interesting. The image of the American president on the screen, sitting at a desk with flowers and family pictures behind him, was, at the least, a novelty.

Reagan was shown on Soviet television during the Geneva summit, but tonight was the first time since 1972 that an American leader has addressed the Soviet people.

The decision to transmit Reagan's greeting was seen here as aimed at maintaining "the spirit of Geneva," the term Soviets use to describe the positive atmosphere in U.S.-Soviet relations after the November meeting between Reagan and Soviet leader Mikhail Gorbachev.

Since Geneva, the Soviet media have continued their constant, often harsh, criticism of American policy, but many have softened their attacks on the Reagan presidency.

Tonight, the family pictures, the flowers and Reagan's congenial demeanor seemed to have the effect of putting to rest the image of the trigger-happy cowboy.

That image, which reached its peak last year before Reagan's reelection, was built up by the Soviet media, but also helped along by Reagan's own quips, such as his joke -- overheard on national radio -- about bombing Russia.

"Even-tempered" was the way one person described Reagan tonight. Another who watched the president at home was struck by the informal pictures of Reagan's wife, Nancy, in the background.

But several Soviets concluded that Reagan's personality was unimportant. "What can he do," said one viewer, a man in his thirties. "There is a whole program -- the Pentagon, the military-industrial complex -- and he is only one man."

As for what Reagan said, one man only shrugged. "Who is to say?" he asked. "We say we are right, they say they are right; we both say weapons are for defense, that our way is the better way. Who can judge? There is no court that can decide these things."