Hey , just to throw that out there, I dont think that you should pick simply what you like, if you are interested in a smooth run through the game.
If you consider the fact that there a 16 starters , the thought that some are better suited than others comes quite natural, especially, because not every type is equally represented in the game to make every starter equally useful.
I finished Episode 14 an hour ago , and I did so using a Todile (Later Feraligatr) , and it was a nightmare. Unless i missed something he only learned one water type move up to level 70 , excluding water gun, which is Aquatail.
His coverage is awful as he learns largely normal type moves. The only move that proved to be quite useful was Ice Fang and even that did jackshit against M3GG4 T3RR4's RAAAAAAAAWRCHOMP , despite Sheer Forde
If you dont want to be forced to use gimmicky tactics , that i find to be usually quite boring , you should use a starter with good base stats , a nice ability , typing and good coverage. Greninja and Blaziken have both proofed to provide just that .
Although for a lack of good TM'S, I would encorage you to pick Blaziken , since that cuts down the power of Greninja a lot .
Since you acces to a big variety of Pokemon types in the early stages of the game is quite limited, you should pick a starter that can deal with the early enemies quite well. Without having tried this , Blaziken should do well . Its fighting type and heavy dmg will help you later , too. I mean after all , there is a reason Speedboost Blaziken was banished to the Uber Tier after all . It just wrecks shit .
In general fire types seem to be superior in the early stages . And later there is enough to choose from to minimize their weaknesses.
Good Luck Mate
Greetings Midget