My favorite is volkner because he is literally too strong to have any fun battles to the point where in the manga him and flint spend presumably days fighting giratina because they thought it was fun. On top of that you can tell he was trying to have fun in diamond & pearl because he throws an ambipom and an octillery with shock wave at you, this man didn't use his real team until pokemon platinum even then he wasn't at his strongest. Also Byron the leader of the sinnoh gym leader have trouble making him act. Norman is favorite in the manga because of his manner his a no BS type of guy, he squeezes phone receivers into pieces he hunted his son all the way across the hoenn region then beat him down in a epic battle on the weather tower. He also does take anything from winona the leader of the hoenn gym leaders(fun fact he is the second most senior when it comes to the gym leader as he failed the gym leader test 8-10 years prior to ruby & sapphire). and last but not least he controlled rayquaza when not even the top minds in hoenn could figure out a way.
As for favorite reborn leader i'd say noel as he adds some realisticness to the ragtag group of people the player can call there friends