where is the most up-to-date debian archive?

[Jim Franklin]

Hi folks,
  I was wondering which debian archive is the most up to date.  I
recently was having trouble connecting to us.debian.org and potato, so
I  included a connect to uk.debian.org (larger bandwidth) in
sources.list.  The potato upgrade from uk.debian.org ran into some
depenence problems because the version of python-base required was a
lower version than was installed on my machine from us.debian.org for
some of the debs.
  This seems to indicate to me that some of the main archives are
updated before other archives.  Is this a mistaken impression?  Which
would be the most up-to-date archives (as far a potato is concerned)?

Jim