To me the Elite seems to be stronger compare to R/S, and there's the cave with Mewtwo to train in.
I forgot about the Mewtwo cave. The Elite is stronger in Fr/Lg but that means it takes longer to go through. I was doing it from the point of having no level 100's yet. When you get level 100's though Fr/Lg is quicker.
I was too.
Even if it is harder, if you have the right strategy, it could go fast.
But then, there is one thing in R/S that did help training:
The secret bases of friends.
I never used secret bases.
Most people don't use many strategies for the Elite. I know people on here do but my friends just train their Pokemon to be really strong and beat them that way. I guess it depends on how you play the game. Whether you use strategies or brute strength.
FR LG ftw! The elites aren't really the best way to train imo, I just train outside the Chansey Dance house in Sevault Canyon. There are 2 cooltrainers with levels ranging from around 50 to 55 and once you're done beating them, you can go heal, run around a bit to charge the VS Seeker and fight them again. My Charizard quickly grew to its seventies against them and that was while I was leveling up some random Pokémon with the Exp.Share for my Pokédex.
I wish I could change my answer. I totally forgot about the vs.seeker. Using that makes the leveling alot quicker.