Yellow version is indeed different than Red/Blue. Whether its harder is up to interpretation. I will say that Gym Leaders in Yellow have far tougher teams. Lt.Surge has a level 28 Raichu with Mega Punch and Mega Kick so a Ground Type Pokemon can't avoid all of its attacks like in Red/Blue while Erika's Grass Pokemon are much higher in level(30 Tangela, 32 Weepinbell, 32 Gloom compared to 24/29/29 and fully evolved too). The real difference is from Koga onward. Koga has his entire team replaced with Venonats and a Venomoth as opposed to Grimer/Koffing line. This makes him more vulnerable to Fire moves being that he has Bug Pokemon while countering anyone who might think Bulbasaur or a Poison Type is worth using because each of his Pokemon knows Toxic and Psychic. To make matters worse, Koga's Ace is level 43 in Red/Blue while in Yellow, his first Pokemon starts at level 44, hence there's a huge jump from Erika to him. Sabrina's line is also redone at are all at level 50 too(again a huge jump in level). However, Sabrina's Abra is shall we say a convenient exploit in that it only knows Flash and Teleport. Therefore anyone knowing that can use a Pokemon with stat changing moves like Double Team to basically charge up while using X-Accuracy to repair any changes to Accuracy from Flash. In doing so, a player can beat Sabrina easily(especially when combined with Generation 1's flawed coding where badges boost your stats while you raise your Evasion). As for Blaine, his team was reduced to three but his team starts out at level 48(one level above his Arcanine in Red/Blue. Speaking of Arcanine, he tops out at level 54 in Yellow). Finally Giovanni... yeah... he's much harder in Yellow. Same deal with Elite Four.
If Nah would ever publish the FAQ already, you'd see this in Generation 1!
