Your addon looks truly awesome. I definitely want to add it.
Their addon may be different because the webservice allows them to access a constantly updated centralized database and, possibly, a machine learning algorithm based on that database. It looks like it might be more similar to Akismet.
For example, I found out about cleantalk by googling the ISP of a spammer that hit me this morning. I found the following awesome page from Cleantalk, the addon we are discussing:
https://cleantalk.org/blacklists/AS55286
Apparently, those IP numbers have been used heavily by spammers recently. Because the info came from Cleantalk, their engineers can use the info to update their algorithms.
With that said, your addon rocks. I like that I could use it to customize my defenses for the specific spammers that are attacking my forum (i.e. their ISPs, GeoIP info, terms, etc.)
Personally, I'll probably go for Akismet because it's in the core and yours because it's configurable, but I was surprised that no one