Continuing the theme from my last post (which was 4.5 months ago!), people are now saying that Facebook's new "pages" features will compete with Twitter (and here)

It doesn't sound like what Facebook is doing will be much different than before, that said, often initially boring changes turn out to have interesting effects. Facebook is essentially improving it's pages system, so that you can follow various brands on Facebook. This is similar in way to going to a company's site and posting a comment on their forum, though without the sign up hassle, different interfaces and presumably I will be able to track replies better. Even with these simplifications, however, it will not be as easy as posting to Twitter. Facebook's approach is akin to looking up something using Yahoo's directory rather than searching for it on Google. On Facebook I will have to find somewhere appropriate to post my message (if it exists) and then post and probably not post if someone has made a similar comment.

User Interface
Twitter's system is, no system. It's the simplest system, since it a text box and button (like Google). So on Twitter I just post. I don't need to read what others said before I post. It's likely my followers haven't seen that yet and even if they have, multiple people saying the same thing strengthens the message anyway. Even though I haven't categorized my message through the power of search.twitter.com people will be able to find it, it may appear as part of a trending topic and someone from the brand can find if they so wish as can anyone else via keyword searches.

Immediacy
I can't imagine that Facebook's system is going to allow quick comments due to not having a limit on the message length and the categories system (as mentioned above). It seems for this reason Twitter is likely to remain the home of breaking news.

Discussion Types
There is another key difference in the way I expect people will use the sites other than the interface. On Twitter I am primary broadcasting messages to people on a variety of topics as they are to me. In Facebook's system, much like in a forum, I will be talking to a community of people that know the topic very well. This will make the process more daunting and less rewarding. For example, imagine going to a Britney Spears group to complain about her music when you know the group is full of Britney's Fans. You still want to make the comment but probably to a similarly like minded set of friends (such as your Twitter friends).

Freedom of speech
On Twitter I can say anything and only I can delete my comments. On Facebook, I expect as in common with most of their site, page owners will control the discussion allowing them to delete comments they don't particularly like. Brands will like this since they have some control, but users are likely to get frustrated by it.

In general Twitter and Facebook are so different I can't see the two competing on this. Twitter is going to have more regular, quicker, critical comments which are publicly searchable. Facebook's method is likely to attract a smaller proportion of it's users, who may in turn maybe more detailed due to Facebook's lack of message length limits and probably less critical.