In Terms of the day-to-day impact on people's lives, the most important office on the ballots Tuesday in Montgomery and Prince George's counties is that of county executiveNewcomers to the area may think "county executive" is just a highfalutin' term for "county manager." It's not. Unlike appointed managers, these executives have independent bases of popular support, plus more authority than many mayors of governors enjoy. Each is responsible for managing a jurisdiction more populous than several states (and, in the case of Prince George's larger than the District of Columbia, as well. Each administers or, in regard to regional programs, heavily influences budgets that add up to over $750 million a year.Each largely sets the tone and direction of county government and wields great influence in regional efforts as well.

While doing so much to shape their counties, the men who rule in Rockvilleand Upper Marlboro also reflect local pressures and constituencies. That is certainly evident in this year's campaigns. The races in Prince George's and Montgomery both turn on personalities more than policies. But the two are very different in emphasis and tone.

In Prince George's county,the question is who can lead the region's most populous and diverse county more effectively toward economic and social stability. During incumbent Democrat Winfield M. Kelly Jr's four years a county executive, Prince George's has begun to emerge from a period of intense racial strain and fiscal uncertainties. The economic develoment that Mr. Kelly has ceaselessly promoted under his personal banner - "New Quality - is starting to pay off.

The Republican challenger, former congressman Lawrence J. Hogan, does not quarrel with the direction of those gains His basic argument is that he can do it better - that Mr. Kelly's performance has been superficial and wasteful, and that new, tough management can take the county farther at less cost during the next four years.

A centralexample involves Prince George's police department, the county agency that most urgently needs to be improved Mr. Kelly and his appointee as police chief, John Rhoads, have made a certain start in recruiting black officers and moving the department away from the the roughneck style that has caused such problems over the years. Mr. Hogan wants to accelerate this progress, by appointing more blacks at higher levels, for one thing. With his credentials as a conservative and former FBI officer, he might accomplish more in this crucial, sensitive area.

On the question of taxes and spending, the choice is indistinct. Both candidates endorse and Prince George's version of TRIM. Mr. Hogan would deal with the resulting crimp in property-tax revenues by curbing spending - though he is also committed to paying for Metro somehow. Mr. Kelly, who has shown a gift for fiscal tinkering, maintains that strict management can enable the county to muddle through without sharp cuts in services.

If Mr. Kelly has done a generally creditable job, as we believe he has, why change? However ironically, the best argument for Mr. Hogan may be Mr. Kelly's greatest success - the advancement of the Democratic/business coalition that totally dominates county politics and policies. Although corruption like that of the 1960s has not reappeared, such tight, prolonged control of any county - especially a large and growing one - is risky on its face. Prince George's voters who want more of the same should stay with Mr. Kelly. Those who incline to the view - as we do - that an energetic new force could be refreshing in Upper Marlboro should vote for Mr. Hogan.

In Montgomery County , the bland style of the primary campaign has carried over into the general-election contest for county executive - with Democrat Charles W. Gilchrist and Republican Richmond (Max) Keeney both playing the politics of thrift. Both have made the seasonally fashionable promises of rigorous fiscal control, elimination of duplicated or unnecessary services, tight budgets - and, to be sure, more responsive government. Given the absence of substantial differences in policies, voters are more or less left to weight the experience of the candidates to arrive at some measure of what each might achieve in the top county office.

Both Mr. Kelly, a former County Council member and a current planning-board commissioner, and Mr. Gilchrist, a state senator and tax lawyer, are considered to be hard if plodding workers. When Mr. Keeney was on the council, he occasionally swung to vote with the Democrats, and he has been critical of some Republican predecessors on the council for their "rash zoning activity." He has said he is not "satisfied" that the present county executive, fellow Republican James P. Gleason, has been as strong an executive as the county's charter-drafters intended. It is true, as Mr. Keeney points out, that the all-Democratic council has effectively checked Mr. Gleason.

Mr. Gilchrist cites his experience in the state legislature, including support of legislative "reform" and ethies bills, and argues that he would be a more effective lobbyist for the county in the General Assembly. In addition, he believes the county executive must do more to represent the county in the region and to the state and federal governments. He would establish monthly town meetings, as Prince George's Executive Winfield Kelly has done.

So the voters of Montgomery County - having already pretty much set the general direction that the office of county executive will take by their primary choices - must decide which of the two is likely to be the most effective. On the basis of his experience in Annapolis and on the regional level, we think the edge goes to Mr. Gilchrist.