Chalk is a delicate subject, there are so many different brands that seem to produce totally different products even though at its base chalk stays chalk.
Beside all the different brands, within a brand chalk can still vary from loose chalk to chunky, liquid chalk or even a block of chalk for example. This is a personal preference and won't really make a difference in your climbing game. Some prefer a super fine powder others like to crush chunky chalk bits in their hands.
The choice is quiet big and can be overwhelming, for a more in depth chat feel free to come down to the shop.