Well you need at least something to play drums (if you want drums) and if what you got is GA4 it is nice to know that you are not limited to the puny library that comes with GA4. With 3. party grooves you can build and save grooves on the pads. That is neat if you go live. The only difference compared to styles is that you do not have the complexity slider. You can compensate by having variety of the grooves on different pads. There will always be more available MIDI grooves than styles. Styles are limitations. Grooves are everything. Unless you do your own drumming. Since GA is soooooo much a smaller product in the market than many competitors my cents is on that there will be no styles from any 3. party. Grooves are more universal (if you get the mapping right).