Hastily written for my own satisfaction.
The trouble with Spacebattles is nothing sticks. Matches with highly controversial arguments get locked, denying the matter a natural resolution. Older threads get locked even more easily. Nothing is ever truly decided and kept moving forward, because the sheer amount of users is too great to allow this to happen.
Like any fiction-debating site, Spacebattles is home to those whom we may wish it were not home to. Those who are difficult or terrible debators. This combined with the aforementioned amount of users increases the chance of undesirable occurences significantly. That is to say, more crap happens.
These users can make their own threads as well, which has resulted in an enormous amount of ill-concieved topics. This also means they get buried, and with them, any and all threads that might have resulted in something good. One may spend weeks on a particularly troublesome debate, but once the dust settles, there will always be dozens of new users who will argue against it the next time without the benefit of having read the previous.
But let's talk about FactPile. It is much smaller, more intimate. Users easily get to know each other. Every time some ignorant newcomer shows up to spout nonsense, it is an event we turn into a learning experience. It is our desire not only to defeat them in fair debate, but also to teach them so that they might make Factpile better.
Factpile is not a zerg-fest. It is a clean, structured environment. My favorite aspects are the community that, due to lack of extreme turnover, can approach each matter with the maturity and wisdom of someone who has made all the rookie mistakes before and knows better, as well as the ability to easily reference past debates and the conclusions reached therein. I also love the layout.
The trade-off is slowness. Not as much happens as rapidly as on debating sites with more traffic, but in turn, this means we are better able to deal with what we do get without becoming overwhelmed. Sometimes weeks go by without us personally finding any matches appealing, sometimes more. But seeing as I debate for fun and personal satisfaction, I say there is no debating site on the web better than Factpile.
And Spacebattles is the Electronic Arts to our Nintendo.