I chose Elesa. Here's why.
For these kinds of comparisons, I imagine that the teams are at the same level. I thus take into account type weaknesses in these analyses.
Skyla has on her team a Swoobat, an Unzefant, and a Swanna. While I like Swanna with Surf (and abuse that move in battle in addition to using it for its obvious purpose), the fact remains that Swanna is a water type, weak to Electric. Also, Swoobat is weak to Electric attacks, and Unzefant. Since all three of Skyla's Pokémon are weak to Electric, I have to say Elesa wins a battle of equal-leveled Pokémon.
To an earlier comment, flinching is not 100%. I got lucky in a low-level battle in another game and got four flinches in a row once in my favour, but it's not always that easy.
Cyclone