I've poked a little bit into the leaks, just to actually see what's up with the starters this time, but it ultimately hasn't influenced my choice. If anything, I'm even less interested in the starter options, even if it's still kinda cool I guess? Even though I know what's up with them, my choices remain the same, so I'll explain my reasoning as if I didn't know. Don't worry about my choice having any influence how you might approach things.
Firstly, Tepig comes off as kinda boring to me, and I want to get a Fennekin for a Delphox anyway, so I'd be eliminating a type crossover that way.
I've not really been all that fond of Totodile, I've used it a few times and it just comes off as an unremarkable physical water type. Gyarados is right there.
So that leaves Chikorita, a Pokemon I've softened up on over the years, but have a generally neutral opinion on. I used to think it was worthless, and it still is the "worst" of the Johto trio, but it is cute so I can't hate it anymore. I may end up dropping it as the game progresses, depends what other grass types the game has to offer.