How they compare
Sis Loves Me and Bratty Sis cover the same fantasy, step-sibling roleplay between adult performers, and both are among the longest-running series of their kind. Sis Loves Me is Paper Street Media's, with 560+ scenes and a new one every week; Bratty Sis is Nubiles', with 500+ scenes since 2017, also weekly.
The bigger difference is what else you get. Sis Loves Me is sold as a Family Strokes membership ($32.99 a month or $149 a year), which also covers Family Strokes, PervMom and Dad Crush. Bratty Sis comes with the Nubiles network ($29.32 for 30 days, $85 for four months or $199 a year), which adds Nubiles' other sites. Prices are at the time of writing.