There are many differences between NBC's monthly news magazine "Weekend" and the hit CBS weekly, "60 Minutes," but one of the key differences is a matter of temperament. "60 Minutes" can be vicious and "Weekend" can be cruel. I'll take cruelty over viciousness any day.

Mike Wallace can run around interrogating the world all he wants to; at "Weekend," airing again tonight at 11:30 on Channel 4, the tendency is to let the world interrogate itself. That one can be virtually poetic in the course of a journalistic statement is illustrated by the splendid opening piece on tonight's "Weekend" show, "Yosemite Summer," about people who think they're getting away from it all even when they take it all with them.

The story is told entirely in acerbic visual terms and through the words of campers whose idea of going back to nature is to load their families and earthly possessions into huge recreational vehicles and lumber off to Yosemitte Park. What they're doing, really is trying to turn nature's spectacle into a TV show, viewed amid all the comforts of home. One man is amazed to discover that mountains are "in 3-D."

Segment producer Craig Leake used the ideal lighthanded ironic touch and came up with a pungent, deflating, hilarious social essay. Space must be made for it in the time capsule - at once.

Other segments on tonight's show include host Lloyd Dodyn's visit to the new, not-so-new Haiti and, during the last half hour, producer Clare Crawford-Mason's forgiving, amusing look at nights and days on the dais for former Agriculture Secretary Early Butz, who it turns out is still telling jokes if not precisely living one.

Ther's talk again at NBC of making "Weekend" a prime-time weekly show, but executive producer Reuven Frank said yesterday that still may be a long way off. "What we're discussing now is how it would differ from the monthly version," Frank said. "I, of course, with my vested interests, would hope 'as little as possible,' but there's talk of everything from a slavish imitation of '60 Minutes' to the same thing we're doing now, only shorter and more frequent.

There are two distressing aspects of this otherwise encouraging development: one is that Lloyd Dobyns may eventually leave "weekend" for the "Today" Show. His personality and the program's are on the same witty and sinister wave-lenght and it's hard to imagine the show without him. Also, there is the danger the "Weekend" will lose the disticnt and disgruntled personality that has made it the best magazine show on TV.

As Mel Brooks said, "Hope for the best; expect the worst."