While they are both etching acids, the Vari-etch Powder and Vari-etch Cream are different in their application use.
The Vari-etch Powder is meant to be mixed with water to form a dipping liquid (like most other dipping liquids on the market- we just don't add the water for you to save on weight, hazard and shipping costs, we figure you can find your own water). Once mixed with water, the Vari-etch powder will completely dissolve and give you a water viscosity acid for completely submerging your glass pieces into for total coverage etching.
The Vari-etch Cream is the same high quality etching acid as the Vari-etch Powder, we've just put it into a cream form that can be used for painting areas, silk screening or etching existing vertical installations and areas that cannot be submerged in a liquid.
Your particular application will dictate which of the two will work best for you.