In terms of dynamics, I think each group worked perfectly well together. Although, I suppose Ash, Misty and Tracey should have had problems the writers didn't pick up on.
I suppose my thoughts of the group with the best dynamics would be either between Ash, May, Brock and Max or Ash, Iris and Cilan. The Hoenn group were pretty well rounded, we had two Pokémon Trainers, one wanting to win the Hoenn league, and the other a Coordinator, we had Brock to do all the cooking, and Max pretty much used that PokéNav to check where they were all the time.
As for Ash, Iris and Cilan. I'd probably say they have the best dynamics out of all the twerps we've seen. There is so much plot potential (and filler potential) around Iris and Cilan, I suppose Cilan even more seeing as he's into almost anything. Cilan pretty much works a lot like Brock did as a cook, only most of the time it's just sandwiches. Iris has proven herself quite useful seeing as she can cook up some medicines if one of the Pokémon are unwell. Overall so far, I think Ash, Cilan and Iris are my favourite group so far, they're just so fun.