XO and Sononym are my main apps. Both are superb.
Sononym excels at finding samples fast, and making full use of my sample library. It’s categorisation is way beyond XO (and Atlas), and it lets you organise LOOPS too (which is huge for me!). I use it to go sample hunting, then drag samples from it directly into Ableton Live (as clips or to Simpler or to a Drum Rack pad) and my MPC. It’s great for creating collated sample collections too.
XO is more of an idea generator IMO for beats/grooves, that lets you make use of your full sample library (one shots). It has sound design tools/capabilities, and lets you export original samples, rendered samples, pattern loop stems, full mix loops and all the related midi files.
It’s a sample groovebox essentially that lets you swap sounds out fast, and has some cool filtering features.
This thread covers a lot of it too;