I chose Froakie because I always go with the water-type starter on my main file for any generation. Overall, I really don't like the gen 6 starters much, though Greninja has definitely grown on me over time, and its potential in battle outweighs my initial negative reaction to its design. I was much more excited about the Kanto starters than I was about the Kalos ones (picked Squirtle to get my favorite Pokémon, Blastoise).
My starter was male, as I always go with male starters because (a) the nickname I use for my starters works better for male Pokémon and (b) blue is my favorite color, and I find the blue male symbol more aesthetically pleasing for my starter than the female symbol. (Plus, for a water-type, blue goes well.) I also wanted to have a starter with decent stats and a non-detrimental/moderately helpful nature, and the first Froakie I found that fulfilled my requirements was male.