Poor Ritual, they get out the door with their (admittedly pretty decent) episodic title first, only to get shown up by the superlative Half Life 2: Episode One a short while later. It's a little early to be declaring victors, especially when Ritual and Valve are allies in the fight for episodic content, but if you're eager to compare the two, now you can do so ... empirically.
Following the 1.4 patch, SiN Episodes is collecting data automatically (but anonymously of course) so they're able to analyze this stuff and (purportedly) create a better game. So, using the recently released data from SiN Episodes: Emergence and the data released for Valve's HL2:E1, we can determine that, in fact, HL2: E1 is the longer game on average clocking in at 5h 23m versus SiN's 4h 49m. The other metrics don't match up as nicely, but there's plenty to geek out over. Hardest level: se1_highrise03. Killingest weapon: Magnum. You get the idea.