Grookey, when fully evolved, becomes Rillaboom. Rillaboom, is a bulky, physical attacker with decent speed, focusing on taking hits with an above-average HP stat of 100 and dishing out hits with a physical attack stat of 125, which is above respectable. If you are very lucky, you may encounter randomly in the wild.
Scorbunny, when fully evolved, becomes Cinerace. Cinderace is fast and physically powerful, excelling at dishing out potent hits before the opponent can attack it. It's frail but incredibly fast.
Sobble, when fully evolved, becomes Intellion. Intelligence, like Cinderace, is very fast, however, it focuses on special attacks rather than physical. If you want to , please choose us, safe and delivery fast!
Again, all 3 of these aren't bad in any way, they're honestly pretty equal. It comes down to personal preference and how it fits in with the rest of your team.