I feel that both sites serve their own purpose and have their own unique personalities.
Of course, haha, as a writer for this site, I encourage every Sega fan to register here. But I also wouldn't dissuade people from using Sega.com...you've just got to tolerate topic after topic of Nintendo hate from certain people. But if you want to engage in real discussion, it's possible at Sega.com, just like it's possible here.