Atlas and XO are both basically drum machines with the extra one-shot sample filtering.
Sononym is much more sophisticated in terms of analysis and categorisation. It makes it very easy to find many sound types, not just drums, and the filters are deeper.
I personally find it much easier to even just “casually” browse my samples because once it has indexed a whole top-level folder, I can still dig down into the subfolders easily and still filter by sound type, frequency content, pitch, harmonicity etc.
Given that many DAWs and plugins/samplers etc can accept drag and drop directly, you can use whatever DAW, sampler or drum machine you like and use Synonym to find the samples. You can even select part of e.g. a loop and drag that out and it will drop just the selected part (having saved the slice in the background).
For £40-ish at half price it’s a very useful utility for anybody who uses samples.