FOR THE LAST decade, Virginia's Eighth District has been represented either by Stanford Parris, Republican, or Herbert E. Harris, Democrat. The tradition will live for at least two more years. This is no great prospect, whatever the outcome of their match-up this time. There are, however, distinctions to be made.

Voters who want their representative to support the Reagan administration's economic policies -- with the usual area-wide stipulation that no congressman of any party will vote against federal employees' benefits, past or present -- will like Mr. Parris. His second term continued a record of undistinguished service marked by his crude provincial attitudes toward the District of Columbia.

Mr. Harris does offer contrast, in the extreme: he comes from the big budget/big jobs/big deficit school. Still, Mr. Harris has been helpful in the past in matters of regional interest. He steered through Congress a Metro financing bill that was crucial to the orderly construction of the subway system. He also worked effectively with members of Congress from Maryland and the delegate from the District. This record of service, in our view, tips the scale.

Voters in the Tenth District have been treated to better choices over the years than their counterparts in the Eighth. And though two years ago, we favored Democrat Joseph L. Fisher over his Republican challenger, Frank Wolf, Mr. Wolf won -- and we believe that, on balance, he has worked hard and well in his first term.

His Democratic opponent, Ira Lechner, is well known to Northern Virginians. A former delegate to the Statehouse in Richmond, he is appealing to those voters who, for purely partisan or anti-Reagan administration reasons, would like somebody else to represent them in the House. But Mr. Wolf should not be tagged as a "rubber-stamp" for administration policies or as one who is afraid to take an important independent stand. He was the only Virginia congressman to vote for the key enforcement provisions of the Voting Rights Act.

It is in service to constituents and to the area that Mr. Wolf has stood out. He has doggedly pushed for a sensible National and Dulles airports policy and for money to rebuild the Filene Center at Wolf Trap. He has joined in bipartisan efforts on behalf of the metropolitan area. His hard work and his efforts to avoid partisan polarization have earned him another term.