Talk about a study in contrasts. Whereas President Barack Obama and Mitt Romney's first debate was largely a cool, technocratic exercise in budget policy, Vice President Joe Biden and Paul Ryan's Thursday night clash involved heated exchanges, emotional appeals and more than one well-delivered barb. Here are some of the salient points:

Biden's attacks: President Obama has waded through a barrage of criticism after appearing detached and uninterested during his debate with Romney; critics wondered why the president did not deploy any of the one-liners he has honed on the campaign trail. Biden did not make the same mistake.

Often dispatched as the president's attack dog, Biden spent much of the debate smiling in disbelief or interrupting Ryan when he disagreed with the Republican vice presidential candidate. The vice president invoked Romney's now-infamous "47 percent" remarks, which were conspicuously absent from Obama's turn last week; denounced Ryan's explanation for the comments as "malarkey" and "a lot of stuff;" and generally offered a rousing defense of the Obama administration's vision.

Ryan's facts: Rep. Ryan has developed a reputation on Capitol Hill as a budget wonk well versed in the nuances of economic policy -- his budget proposal has essentially formed the foundation for the Republican Party's economic platform -- and he showed on Thursday that he had done his homework. Ryan managed to work in a few zingers of his own ("Mr. Vice President, I know you're under a lot of duress to make up for lost ground, but I think people would be better served if we don't keep interrupting each other"), but he was largely more reserved.

While the Wisconsin Republican at times seemed rattled by Biden's aggressiveness, he was prepared for most of the vice president's points with well-rehearsed rebuttals: He was able to cite the economy's slowing rate of growth over the last few months, for example, or to point out how much funding higher income taxes would put into the economy.

A sparse Republican budget plan: Jim Lehrer was widely faulted for his moderating performance last week, with many observers saying he simply let Romney and Obama joust without interrupting or seeking clarification. Martha Raddatz did better on Thursday, doing her best to cut through the crosstalk and sometimes halting exchanges to ask pointed questions. This was best demonstrated when Raddatz asked Ryan how the Romney budget plan would pay for a 20-percent across-the-board cut.

"Do you actually have the specifics?" Raddatz asked Ryan. The vice presidential candidate repeatedly deflected the question, ultimately contending that Congress would work out the details. It was a markedly different outcome from last week's debate, when Obama repeatedly pressed Romney for details on how his plan would be deficit-neutral -- “It’s math. It’s arithmetic,” the president said as he tried to show that the Republican blueprint wouldn't work -- but the Republican nominee largely wriggled free. 

On foreign policy, little daylight: Romney and Ryan have continually assailed Obama for pursuing a foreign policy that they say emboldens America's adversaries while undermining its allies. But Biden pushed back hard on that characterization on Thursday night, demonstrating that Romney has rarely offered clear alternatives.

"What would my friend do differently?" Biden asked as Ryan attacked Obama's handling of Syria. "If you notice, he never answers the question." The vice president argued that Obama has marshalled worldwide support for crippling sanctions on Iran -- the type of international consensus that he said Republican bravado would have harmed -- and said that, short of military action, Romney had no alternate plan. Biden also dismissed as "a bunch of stuff" the well-worn criticism that Obama has ignored Israeli Prime Minister Benjamin Netanyahu, questioning how a president Romney would act differently.

Elderly voters matter: Inevitably, Medicare came up -- inevitably not just because Ryan is the architect of a plan to restructure the cherished program, but also because Medicare is of supreme importance to older voters, who tend to show up at the polls. Some of the debate's most animated moments came as Biden and Ryan defended their respective campaign's Medicare plans, invoking personal stories to demonstrate their commitment to preserving the health insurance program.

Biden, his silver mane juxtaposed with the younger Ryan's black hair, appealed directly to that crucial voter bloc in arguing that Ryan's plan would drive up costs for seniors. "Folks, follow your instincts on this one," Biden said, looking directly into the camera. At another point, he defended the Affordable Care Act's Medicare provisions, again gazing into the camera as he responded to Ryan's point.

"Look, folks, all you seniors out there, have you been denied choices? Have you lost Medicare Advantage?" Biden asked.