This is an interesting group of players and all of them are quite comparable to each other.
Additionally many of them are the ones who interacted (in battles) with each other intensively.
Trebol - He has a disgusting ability. His beta beta no mi isn't a skill pleasant enough to look at. I have always disliked his devil fruit. Putting that aside, he is quite a good fighter. It was very impressive when he killed a fly without even a fling of his eyebrow, while Leo was trying to get near Sugar to put the "grape" into her bowl. But Robin stopped the operation. She felt that though Leo's speed was fast, Trebol's speed was even faster.
In the case of Sugar, she is often mistaken as a child though she is much older. Somehow she stays in her child form due to the effect of her devil fruit. I always recalled during the time when Sugar was trying to get close to Luffy and Law who were talking/arguing and did not really take notice of her until she finally drew near. For Luffy and Law who did not know Sugar, it was natural for them to think that she was a child and hence harmless. Little did they know till later that Sugar had such capability to turn so many humans into toys and cursed them into slavery. I can imagine those opponents being turn into toys and become her slaves if they do not know what this "little girl" is capable of.
In terms of physical ability, she will lose to everybody else. Her only advantage is when someone comes close within her reach where she can touch and turn them into toys.
For Robin, she is actually very good in her devil fruit. She has been a formidable fighter since as a child, then as Miss All Sunday and finally being part of Straw-hat. She is someone who has gone through many kinds of trials in life, and learns the hardship day by day. Her hana hana no mi has gone through training after training and she seems to have mastered it very well. She can crash someone's neck to kill, or creates a giant ladder as a form of escape, as seen in Dressrosa. It is definitely a useful skill to have.
Next, Kyros has been very powerful since the time when he was first introduced as a toy. As a toy soldier, he had been skating around, helping to train his daughter, Rebecca, fighting skill, till she grew up. He was already very impressive since then but when he regained his human body, he continued to be his daughter's protector and defeated Diamante finally. At that time he only had one leg.
Leo is part of the 5600 army and he is one of the seven captains. He seems to have mature in his thinking now. I hope he isn't as gullible as before (same for the entire Tontatta tribe), or he may lose this battle.
His devil fruit is pretty useful in many situations. The first time it was used was the time when Robin and Nami stepped close to the Tontatta territory and Leo sew them onto the ground. The recent one was Leo sew all the Marine ships together. I was amazed that he could sew metal.
Besides his DF skill, he is also very agile and good in speed. That was why he was so confident that he could drop the "grape" onto Sugar's bowl. As long as he maintains his composure, he should be able to win.
In terms of my choice, I would choose Robin as I find that her DF skill is both defensive and offensive. As long as it is not fist fight, then she should be able to make use of her DF in an efficient way. Moreover she appears to be a person who has a calm and logical mind and she is able to analyse various situations before she acts on them. I guess Robin being an archaeologist isn't just a name after all. She is also able to use things or people around her to her advantage.
The second person I wanted to choose initially was Trebol, but I changed my mind. Though his ability has scored many good points and it is also very powerful. But his arrogant attitude would probably be his downfall. Thus I have decided to pick Leo. If Leo didn't become part of the seven captains, I probably may drop him. In view of his new role, I believe he should be considerably very important to the future arc. At the current Dressrosa arc, he has already shown how skillful he is and if he wants to advance further into the New World, then he would need to improve on his skills. From what that has been seen, he has always been the leader of the Tontatta army and his leadership skill is pretty impressive. The whole tribe actually depends on him. Besides his DF, his physical strength is beyond imagination. No one would have thought that such little people (the dwarfs) would possess such powerful strength. Even the giants may take their hats off. Another thing about them, they are so small that you can hardly see them and I reckon that it is going to be a disadvantage to the opponents when the dwarfs attack. Leo in this battle may be able to gain the upper hand.
Let's see what are your choices.
who comes up with these groups , lol. 
