When I was younger, I had a difficult time getting through Victory Road in Yellow because I wasn't aware I could push the boulders down the holes in order to create paths XD I thought there was no way out, and I hated how I kept encountering wild Pokemon (I wasn't smart enough to use Repels at the time).
As for training, I've only really trained Pokemon in Victory Road in FRLG and GSC. Given, I still had trouble training Pokemon in FRLG, since it felt like it took forever for them to level up. (They were definitely at higher levels, but I still had difficulty fighting the Pokemon League with them.) It was also sometimes hard beating some of the Pokemon if you didn't have any moves that were super effective against them, especially since quite a few found in FRLG's/GSC's Victory Roads were defensive. Not really fond of training there otherwise, especially since there are ways to battle Trainers, especially in the later games (e.g., the Battle Chateau and restaurants in XY and the sports domes in BW/BW2). You get experience AND money (and sometimes items), plus you don't always have to worry about wild Pokemon, so it's much better, in my opinion.
As for training, I've only really trained Pokemon in Victory Road in FRLG and GSC. Given, I still had trouble training Pokemon in FRLG, since it felt like it took forever for them to level up. (They were definitely at higher levels, but I still had difficulty fighting the Pokemon League with them.) It was also sometimes hard beating some of the Pokemon if you didn't have any moves that were super effective against them, especially since quite a few found in FRLG's/GSC's Victory Roads were defensive. Not really fond of training there otherwise, especially since there are ways to battle Trainers, especially in the later games (e.g., the Battle Chateau and restaurants in XY and the sports domes in BW/BW2). You get experience AND money (and sometimes items), plus you don't always have to worry about wild Pokemon, so it's much better, in my opinion.