well for me theres a few.

one is upgrading since these skimmers are rated for such a wide rating and the body small i am going with a dc skimmer for 75 g cubes and if i upgrade i just turn it up to a faster speed, i havent had a chance to put this to use yet but we will see.i use a r10-i at the store on a 400g system and its outperformed my expectations so far.

the variable speed also helps tune the skimmer

i know if i run it on a low setting say speed 2-3 and i have an issue with a bubble tip ending up in my powerhead then having the ability to turn my skimmer up helps alot as well.

the amount of air and water these take in massive , so if i am treating with something that requires extra oxygen in the water i can take off the top , turn up the rpm's and increase the amount of air.

cleaning the skimmer neck is easy with a 10min feed push button that doesnt need to be pushed again to restart.

i like the fact that these pumps ramp up and down to speed so they have a soft start:)