18% Nickel / Silver Fretwire vs. Stainless Steel Fretwire
The standard fretwire found on most guitars is 18% Nickel / Silver. Despite it name it's actually made from a composite of mostly brass with a lesser amount of nickel added. It's easy to work with when doing a refret, has a silverish color, and is the choice of most manufacturers for use in the construction of their product.
Stainless Steel is much harder and lasts much longer. It has an appearance that resembles chrome more than silver. It's harder for a luthier to craft / bend / use during a refret. If you choose this type of fret to use for a refret expect the luthier to charge anywhere from $50 to $150 more for the work involved.
Besides a difference in look and life expectancy some players note both a slightly brighter tonality on guitars fitted with Stainless Steel frets as well as a more pronounced feel to the frets as they maneuver their fingers on the fretboard.