Does anyone know which is better to use? 

I know with the one from SMF you can have each database seperate, but that's all I know.  Trying to find more info.

Oh heck, I'll take a stab at it...

Off the top, I don't recall all of the various technical differences. I often have to peek "under the hood" of software because I usually have to tweak and customize. But, the typical person is more interested in functionality and couldn't care less about all the techie details. So, I'll discuss this in terms of what the bridges do.

With respect to which one is better question, I get that asked all the time, and I'll give my standard answer...

It depends upon exactly what you want to accomplish.

I've used both bridges. In a nutshell, the reason I ultimately chose JSMF wa that it seems to be more dedicated to interfacing with 3PD products like CB. I am working on several real world projects where social networking and interactivity are critical features, and for Joomla that generally means CB is part of the solution. To that end, JSMF has implemented features the other bridge has not. For example, the ability to select which profile and messenger to to use.

Another critical thing for me is the nature of the team who backs the product. SMF has a lot of wonderful built-in capabilities that are yet to be fully harvested. I'd even made a feature recommendation on the SMF boards that the forum's Profile feature is a potential powerhouse that needed to be more easily accessible to outside programs (such as Joomla). Nothing officially was done. However, in contrast, the JSMF team appears dedicated to making SMF extensible to other products (i.e., CB).

Again, in no way is this a criticism of the official bridge. Just that what's "best" is determined by what's needed, and JSMF fulfills certain needs.

Hope this makes sense.

Regards,
Brat.