I thought the topic was interesting and while the World Tournament Junior Cup hasn't started yet, and opinions may change in the process, we can still make comparaisons based on what we know about the two tournaments.
Mikuri Cup being great because it served as a culmination of an arc that started in Yosuga City. During this arc, Hikari was broken down as a character, slowly built herself up by learning more about contests, getting more battles under her belt and working on getting over two flaws she was established to have since the beginning of DP. Her overemphasis on moves rather than Pokémon, as in a flash over substance, and her lack of confidence that lead her to quit things at which she didn't believe in herself (like how she released Pachirisu because she didn't believe in herself enough to be its trainer.) The way the cup was written is geared towards Hikari exorcising her issues. First up, with her appeal showing her growth with Eteboth and getting more and more confident with each battle until she wins, realizing she can do it and be great if she believes in herself. Not only was this a very compelling journey, but there's actual substance in her victory.
From what we know of the World Tournament Junior Cup, there is no such substance. With the Mikuri cup, the writers built upon solid foundations they had previously laid out. Here, the foundations are less solid and in one case, inexistent. I think Shooti needed to win this tournament and Satoshi needed to go far, not only to reignite their rivalry and hype the League, but to further define how Adeku and Satoshi's philosophy clashes with Shooti. So I don't mind that the tournament seems to be building up to these two, because it can take their story to the next level, and they both need it. They have the perfect occasion to really flesh out Shooti, and I don't mind them taking it. That being said, while I think that Shooti and Satoshi making it to the finals is justified, and hopefully it'll be more compelling than their previous encounters, the way the rest of the tournament seems to be going down looks to be complete nonsense, namely Iris.
Contrarily to Hikari in the Mikuri Cup, Iris has no foundations. Last weeks episode was about how much she doesn't have flaws, is better than everyone else and his so skilled at training Dragons. There's nowhere to go with a character like that, except to create faux-drama where she's in trouble but it's not her fault, there's no consequences and it gets resolved super quickly throwing two characters under the bus in the process. There's just absolutely no reason to have Iris get pass the first round with a Pokémon she hasn't trained, just caught fully evolved (not because she defeated it but because it realized how much of a pure radiant saint Iris is and wants to throw away his life as a wild Pokémon to be her pet fully evolved Dragon). Had Iris trained and evolved her pokémon like everyone else, then maybe, but this is just flying in the face of the whole message of the show, it isn't earned, it isn't the result of anything. It's just Iris getting once getting rewarded for sitting on her hands doing jack. She really has no business beating Langley or Hikari and that we're once again focusing on her character, when the writers really have shown nothing in the form of a story for her, instead of developing the characters who need more spotlight is just disappointing. That's something else the Mikuri Cup did: it didn't allow characters who had no business getting far go far, like Satoshi losing in the quarterfinals to a nobody. But in Iris' case, it's not the culmination of anything, it's not leading to anything, it's just gratuitous glorification that has no purpose and just kills this tournament.
Plus, they made sure that Haruka really had her time to shine both in defeat, but also in the appeal round and in her match against Nozomi. They really did her justice, which doesn't look to be the case with Hikari in the Junior Cup. Rather, they threw her a couple of unfinished ties with Dent and Satoshi and what looks to be a quick match against a CotD in the first round, and a second round loss against Iris, that really doesn't feel earned story-wise.
Funnily enough, when Hikari had no control of Manmoo in a contest, she lost that contest because she wasn't ready for it. She had to work on Manmoo's contest style more. Here, there's no consequences to Kairyu's disobedience, there's nothing really happening with it and it gets resolve during the battle against Hikari. That the writers introduce a problem, but don't allow it to have any consequences nullifies the problem and any development. There's no change to Iris' character since she's already a Dragon Master, already knows everything there is to know about Dragons and only has to wait until Kairyu realizes he can't win without her. Yawn.Iris here only technically beat Dawn in the previous episode because her Dragonite did everything as a wild Pokemon.
Overall, I think the Mikuri Cup was handled much better than the Junior Cup looks to be.