git repack vs git gc --aggressive

hello,

I read this:
  http://metalinguist.wordpress.com/2007/12/06/the-woes-of-git-gc-aggressive-and-how-git-deltas-work/
where
  git repack -a -d --depth=250 --window=250
is mentioned as a (recommended) alternative to git gc --aggressive.

I am a bit confused, because the page also mentions that git gc --aggressive is recommended when a repo has been imported using git fast-import.

So my questions are:

1. is the above repack command (with --depth=500) safe? Of course I want
   to be absolutely sure that our repo will be consistent.
   Do I need another command ("git gc", "git prune") as well?

2. is it the right tool for the job or shall I use git gc --aggressive?

Thanks!