There are multiple types of filter circuits. But I want to talk about the format of the filters.
Here are some of the major configurations.
Can the filter self-oscillate? By turning up the resonance does the filter begin to generate its own sign wave? Some do and some don't.
Does the filter bass compensate for higher resonance levels. You'll find with a lot of filters, you lose low end as the resonance goes up. This isn't a good or bad thing. But just the nature of the beast. If you want high resonance with a bass sound. This might come into play.
Outputs. When dealing with a multi-mode filter, how are the outputs structures. Some modules put all the filter types on separate output jacks and all filters are simultaneously available. Others use only one output and the user selects (usually on a switch) which filter feeds the output.
Input (levels). Some filters have input level controls. How hard your signal hits the filter can alter the sound significantly. So an input level control might allow you to adjust things to your taste.
Modulation. This can range from simple CV control over the cut-off point or you can get into modules with multiple controls including the afore mentioned FM control (linear and exponential), 1/V Octave tracking, CV over resonance, and even some exotic controls like ping, mix levels, even control over filter type.