You hit the nail on the head. Baby Daisy instead of Waluigi is only the better if you're already good at the game. Using her snaking drifting technique will only save time if you're one of the top speedrunners.

In multiplayer and online, having low weight is a bad thing in competitive play, as you can easily be bumped into walls or off the track. Most competitive players will use a combo with more speed, Waluigi on Wild Wiggler/Azure Roller/Paper Glider (the same one as the Mario Kart Stadium world record).