Froakie - Greninja
Froakie is a bit fast for a starter with a base speed of 71. The rest of his stats are trash. When it evolves to Greninja however, it gets WAY more powerful. Greninja is so fast with a base speed of 122! It is also an awesome special attacker with 103 base special attack! The problem about Greninja is its defense is terrible at a base 67 which is awful, but Greninja is very fast and packs a mad punch so it wouldn't matter a whole lot for defense, unless some electric types get in you way, that would be bad... Greninja's stat total is 530
Litten - Incineroar
Litten's speed stat is pretty good with base 70 and as always when it comes to some starters, his other stats are garbage. When he evolves to Incineroar though, he gets a lot better. Incineroar is an awesome special attacker with 115 base attack. The real problem is its speed stat, it is surprisingly WORSE than Litten's at a base 60, so he is very slow. The rest of his stats are pretty decent. His stat total is 530 as well.
Comparison: So both have the same stat total, so we can't judge by that, both are very well in what kind of attackers they are, but when you look at Greninja, he is way faster and packs a mad special attacking punch. Even though his defense is trash, it doesn't really matter because of the awesome speed and special attacking stats. So I would recommend Greninja to be on your team!
I hope this helped!