By Bertrand Benoit in Berlin and Brian Blackstone in Frankfurt 

Germany, the biggest opponent of the European Central Bank's new stimulus program, is poised to reap immediate benefits from the effort--an irony that underscores the complexities of designing one monetary policy for the 19-member currency area.

The ECB's program, unveiled in January in an attempt to shake the eurozone out of its economic torpor, drew cheers from many investors, politicians and businesspeople from the region and around the world.

But in Germany, Europe's largest economy and one of the Continent's healthiest, the decision was met with disapproval from political leaders and the public alike. That is even though the country's export dominance, well-capitalized banks and strong labor markets provide its economy the best conditions in Europe to channel the central bank's easy-money policies into borrowing, spending and output.

The president of Germany's traditionally conservative central bank, Jens Weidmann, says the ECB's massive stimulus would fail to address the eurozone's debt and competitiveness problems. The program, he warns, would take pressure off countries such as Italy and France to revamp their labor markets and push through other economic overhauls. Chancellor Angela Merkel, as well as much of German media and industry, has stressed the same point.

Germany's opposition, in part, reflects the economic disparity that has complicated the ECB's task of formulating a single monetary policy for 19 mismatched countries. It also highlights a persistent philosophical disagreement between Germany and most of its fellow eurozone members about how to tackle the crisis that broke out in 2010.

Berlin's experience with overhauling its own rigid labor market and trimming the welfare state in 2003, and the long and relatively robust recovery that ensued, have played a key role in its insistence that other eurozone governments do the same.

Benefits of the stimulus may pale against long-term risks, critics in Germany say. "It's not necessary to flood the entire eurozone in order to fight fires in individual countries," says Karl-Ludwig Kley, chief executive of German pharmaceutical company Merck KGaA.

"Germany has always had a long-term horizon and has been more critical about the second- and third-round effects" of policies, says Dirk Schumacher, senior European economist at Goldman Sachs. "Others have tended to say: 'Let's deal with the side effects later.'"

Given the growth-boosting effects expected from the ECB's quantitative easing--from rising stock and property prices to easier credit conditions and higher exports--Germany's opposition has left some economists perplexed.

"It's a big puzzle," says Prof. Marcel Fratzscher, head of the Berlin-based DIW Institute for Economic Research and one of the few prominent German economists to welcome the ECB's announcement.

German markets have applauded the ECB's move. The DAX index of blue-chip listed companies has appreciated by almost 10% this year and almost 5% since the quantitative-easing program was unveiled last week.

Anticipation of the bond-purchase program has driven a massive rally in German government bonds. Ten-year yields, which were above 1% as recently as late September, touched a record low of just below 0.3% the day after the ECB meeting. Yields are negative up to maturities of five years, meaning investors are effectively paying Germany to borrow.

Stimulus plans have also had a dramatic impact on the euro. The currency has fallen more than 15% against the dollar in the last six months to trade at around $1.13--a development that will help German exporters.

In a theoretical model assuming a 10% fall in the euro against a basket of other currencies, the eurozone's $13 trillion economy would gain 0.3 percentage points of growth, Carsten Brzeski, economist at ING Bank, estimates.

But the effects would vary widely. Germany and the Netherlands, which export extensively outside the eurozone, would see the biggest boosts--0.5 percentage points or more to growth in gross domestic product--while the weaker economies of Spain and France would benefit less.

Economists at Nomura see Germany benefiting about twice as much as France from the euro depreciation. With foreign trade accounting for more than 70% of German GDP, exports are vital to the country's wealth.

According to Gert Peersman, a professor of economics at Ghent University, a 2% rise in the amount of assets the ECB holds raises German GDP by around 0.3%, about twice the effect that Spain and Italy are expected to experience. The reason: Germany's banks are better capitalized than many of their European peers, allowing them more leeway to lend.

German households, too, seem better positioned to channel the ECB's largess into new spending. In January, consumer confidence hit a 13-year high according to data released Wednesday by research group GfK, while it was flat in France and well below its long-term average.

Other German asset classes also stand to benefit. Property prices in Germany fell between 2001 and 2007 but are now rising by up to 10% a year in some cities and with household debt low, they could go further.

German critics of the ECB object that those rising asset prices will have a limited effect. Just over half of German households own their homes, according to the Organization for Economic Cooperation and Development, well below the 71% European average. While low-yielding government bonds remain popular, stock ownership is falling.

That is part of the reason why many Germans oppose stimulus plans. "Essentially, the bottom 60% of wealth and income distribution have their savings on their savings accounts," Prof. Fratzscher says. "Given the current interest rates, building wealth is impossible for them."

Josie Cox

in London contributed to this article.