Electropolishing and passivation are very different processes, and to decide which is better for your needs, you should know what these differences are.
Passivation is a chemical process that eliminates free iron and ferrous contaminants that are embedded in stainless steel parts during manufacturing, returning those parts to their original corrosion specifications. Electropolishing is an electrochemical process that treats a wide variety of alloys, including stainless steels, aluminum, copper, brass, titanium, Nitinol and many others, including specialty alloys.
Electropolishing is the more aggressive of the two operations, as it dissolves a uniform layer of surface material from a metal part. This eliminates not only embedded contaminants, but imperfections like mirco cracks and pits that become initiation sites for corrosion. This process makes electropolished parts as much as 30 times more corrosion resistant than passivated parts. Electropolishing also removes oxide scale and heat tint created by manufacturing, which passivation does not. Ultimately, electropolishing is a more comprehensive, versatile and effective process.