The simple difference is that the old filters didn't work very well and the new filters do. When a filter isn't stopping your spam, it's easy to conclude that the problem is that your spam is special, and the filter needs to be adjusted to know about your special spam needs. But it isn't stopping your spam, the reason is really much simpler: It's because it's not a very good spam filter.

Although there are plenty of theoretical arguments about why some people might consider a given message to be spam and others wouldn't, the reality seems to be that we all agree what's spam and what's not. For the few arguments where people differ, the differences are not great and the messages in the grey area tend to be ones that people wouldn't object to receiving, but wouldn't care if they were lost, either. (Think newsletters from companies from which you've bought stuff.)