6th Gen deciding on team members

This isn't as much of a reply as it is my own question. I'm struggling in pokemon x with deciding for a 5th and 6th pokemon to use. So far I have greninja, charizard, lucario (caught as riolu) jolteon and krookodile... I want an arrgon (I'm considering swapping krookodile or jolteon) and am considering Salamanca...but i don't know lol there's so many options.

Yeah, sometimes it can be hard to choose when there's so many fun options

But I think that you'll want to keep Jolteon, since you'll need something for the Water Elite 4 member. So if you're going to replace something with Aggron, it should probably be either Lucario or Krookodile. Or you could even just have it be your 6th slot and not use Salamence.
¯\_(ツ)_/¯

I would recommend just going with your favorite pokemon or ones you like a lot. During playthroughs, unless you are having a lot of trouble, just use the pokemon you have the most fun with.

Get a Sawsbuck (if possible)