THERE IS nothing too difficult about the choice offered in Maryland's contest for the U.S. Senate. Paul S. Sarbanes has served the state intelligently, with a keen perception of how local, state and world affairs affect the voters of his state. Little in the campaign of Republican challenger Lawrence J. Hogan has offered Marylanders reason to alter their current bipartisan representation.

What makes a difference in the Senate is an ability to grasp the big picture, to sense and mesh the various concerns of constituents and reflect them in some consistent manner. Mr. Sarbanes is noted for this sort of approach. It does not lend itself to an easy "liberal" or "conservative" label. Consistent thoughtfulness is a more reliable index, and it is here that Sen. Sarbanes makes his mark.

When Mr. Hogan campaigned for his current office of Prince George's county executive, he held promise as someone who might work effectively with different factions at the local level. He did make long-overdue improvements in county law enforcement. More commonly, however, he fell into stubborn and unproductive combat with the all-Democratic county council.

This same tendency may account for the absence of a substantive campaign by Mr. Hogan, whose main messages seem to be scatter-shot attacks on Mr. Sarbanes' low-key style. Mr. Hogan couples this with vague appeals for the support of supposedly discontented people. If there is a sense of direction or a grasp of complex issues here, it is well disguised.

Mr. Sarbanes is sometimes cast as aloof or unproductive. But he has crisscrossed Maryland, articulating a quiet, serious-minded concern about unemployment, farm failures, bankruptcies, weakened environmental policies and the state of retirement and Social Security programs. To his credit, he has avoided expensive, quick-fix proposals.

For his service, he wins exceptionally high marks, and he deserves reelection.