I think I'll use a mix of old and new. Outside of the starters, I've tried to avoid learning about too many of the unannounced new Pokémon from the leaks (I've seen images of some, seen names for others, and know nothing about some of them), so I figure I'll try different Pokémon as I go along. Given comments about the Exp Share, I'll probably use more than six Pokémon in my rotation again this time, so I figure I'll try out a bunch of the new Pokémon and see if any of them stand out to me. I like to give as many Pokémon a chance to impress me as possible, both old and new.
My current thoughts include:
-Sobble (my planned starter)
-Maybe the other starters. I would like to use Grookey. I might try Scorbunny, though I'm not overwhelmed. Frankly, I would probably be happier using Charizard as my fire type, though my impression is that I might get it too late in the game unless I trade.
-Pikachu. Pikachu is my second favorite Pokémon, and I pretty much always use one on my team. I might go with the Let's Go Pikachu-linked one, but I'm not sure yet.
-Other team members TBD, pending trial. I might throw in a couple of old favorites from my Gold team, like Noctowl and Quagsire.