As mentioned, Chrome is definitely the shinier of the two mentioned finishes.
Just to add a few more things.....nickel is shiny when new too, but has a slightly more yellowish hue, while chrome is more bluish.
As for ease of maintenance, the trophy goes to chrome.
Nickel, although full of vintage vibe, has a bad habit of tarnishing and going dull, more so than chrome.
Two of my basses have nickel plated machine heads, and one of them has a nickel plated Badass II.......hard to keep shiny, man. :?