The reason it's the best article, yet, is because Sirota went into an analysis of what a Ron Paul presidency would likely be able to achieve, given the very real constraints of Congress. And constraints that are not just dictated as such, theoretically, by the Constitution, but as actually practiced.
From Who’s a real progressive? Obama and Paul both hold positions anathema to liberals. Voters need to choose which ones to overlook
Hence, we reach one of those impossible questions: From a progressive perspective, which is a more legitimate camp to be in? In terms of ideological allegiance to the larger progressive agenda, I don’t really think there’s a right or wrong answer. But in terms of realpolitik, there’s a strong case to be made that Paul’s progressive-minded supporters understand something that Obama’s supporters either can’t or don’t want to: namely, that a presidential election is a vote for president, not a vote to elect the entire federal government. As such, when faced with candidates whom you agree with on some issues and totally disagree with on other issues, it’s perfectly rational — and wholly pragmatic — to consider one’s own multifaceted policy preferences in the context of what a prospective president will have the most unilateral power to actually enact.
With Paul, it just so happens that most of the ultra-progressive parts of his platform (and legislative career) correspond to the presidential powers that are most unilateral in nature. As President Obama so aptly proved when he ignored the War Powers Act during the Libya conflict and started drone wars in various other countries, a president can start and end military conflicts with the stroke of a pen — and without any congressional check on power. Likewise, as President Obama showed when he assassinated American citizen Anwar al-Awlaki and then his family without so much as a single criminal charge, a president can now trample or expand civil liberties with the stroke of the same pen. The president also appoints the chairman of the Federal Reserve bank, which now unilaterally grants trillions of dollars in bailouts without intervention from Congress. And, as President Obama proved with his administration’s crackdown on California’s marijuana laws, a president has far more operational control over the drug war than the congressional committees charged with oversight.
By contrast, the policy areas where Paul is most at odds with progressives are the areas Congress has far more control over — specifically, budgets and regulatory statutes.
N.B.: Other articles or presentations by prominent progressives that sought to rationally evaluate, from a progressive perspective, Paul's candidacy vs. Obama's, include those by authors Glen Greenwald*, Matt Stoller, and Cenk Uyghur.
N.B. #2: My own diary on this sort of analysis is What horrors, from a progressive POV, would a President Ron Paul ACTUALLY be able to achieve?
* Greenwald's wikipedia page says that he's not liberal or conservative, but takes a bit of both sides' positions. He seems more progressive than most.