What's more common? Re / Im or Fraktur-R / Fraktur-I for real / imaginary part?

Title says it all. What's more common? Is there one to prefere (maybe due to some norm)?

This:

$\operatorname{\mathfrak{R}} z, \operatorname{\mathfrak{I}} z$

or that:

$\operatorname{Re}z, \operatorname{Im}z$ ?

-
It's not "fractal". It's "fraktur". Wikipedia. –  kahen Nov 10 '12 at 15:55
Thanks, corrected. –  Foo Bar Nov 10 '12 at 15:58
This is an opinion question which is hard to answer. My own sense is that the fraktur notation is a bit older and less common nowadays. –  Grumpy Parsnip Nov 10 '12 at 15:58
Also, the correct "LaTeX-y" way of writing "Re" is "\operatorname{Re}" (or "\DeclareMathOperator{\Re}{Re}" in the preamble). See: tex.ac.uk/cgi-bin/texfaq2html?label=newfunction –  kahen Nov 10 '12 at 16:02
Because of Latex I'm actually here. I was wondering if there's a special reason why Latex defaults \Re and \Im to the Fraktur versions. –  Foo Bar Nov 10 '12 at 16:05