Tiffany! I think I would like
Brittany a lot more if it were pronounced with three syllables. BRIT-nee just sounds so insubstantial and cheerleader-ish to me and the alternate spellings of
Britney,
Brittney etc. make it seem even less substantial. Also
Brittany has a short history as a given name and is a region in
France (which is called Bretagne in French).
Tiffany has a more interesting history as a given name having been given to girls born on the epiphany and it has been used for a long long time. It also has more strength to me because its alternate spellings didn't become common, unlike
Brittany's. I get a bit of a cheerleader vibe from
Tiffany too but I guess that's only because it was so overused in the 80s, but less overused than
Brittany in the 90s.