Actually, they should be compared, but not for that reason. They should be compared because of unintended consequences. Bomb them too much, and you get Assad out of there, which in one sense is a good thing, since he's a murderous thug. However, the rebels are largely even more murderous thugs from Al Qaeda, who would represent an even more immediate threat to the US. Since Syria as it stands doesn't threaten us at all.
An even more immediate comparison was Obama's leading from behind in Libya, where we also had no pressing national security interests, but he wanted a war of his own anyway. But one he could fight from 30,000 feet. We know where that got us, a dead ambassador for the first time since Carter, and other dead Americans, a scandal, and thousands of heavy weapons including Stingers dispersed to who knows where, (Syria and AQ being one good bet).
Obama has no plan, no idea even of what he wants to do, and no idea of what he'd be setting loose.
There may be a security interest in punishing the Assad regime for using chemical weapons. As far as I know, no government leader has used them since Saddam did in the late 1980s against the Kurds. People have been talking about the establishment of a chemical weapons taboo for the last 25 years. Beyond immediate humanitarian concerns (which are important), it may be wise to rebuke Assad for breaking the taboo. That way, we discourage other countries from using them or supplying them to terrorist groups.
As for Obama lacking a plan, that's a silly point. I'm sure the Pentagon has provided him with multiple strategies. It always does. The generals war game everything. It's up to the president to determine which is the best strategy.
This case, I think, is very similar to Libya: there's a humanitarian crisis that the world is watching. The U.S. loses credibility as it sits on the sidelines and allows tens of thousands of civilians to die. But it risks making the situation worse by intervening. Islamist groups could gain control and turn Syria into a terrorist stronghold. People in the region may interpret the intervention not as a humanitarian mission but as an imperial project. No doubt, local governments will spin it as such to foster deeper resentment against the U.S. Or possibly, military strikes by the U.S. could make the Assad regime even more desperate, encouraging it to increase rather than cease its use of chemical weapons.
The Syrian situation is without good options, I think. So Obama will ultimately make the "wrong" choice, but only because there are no "right" choices. So the question may be whether he makes the least bad choice. And because I don't know enough about Syria, I'm not sure what the least bad choice is.