RL is great for such things as bezels, transitions, easily changing/setting different emulator options to be used, utilizing its configurations for changing controls, custom scripts, easy ability to use with multiple frontends so you don't have to set up each one separately. List goes on and on and on. RA is easy to config, add it as an emulator, direct it to the cores and launch a game, set up your configs for that system and save them and rename that file to match the name of the system in RL.