[tor-relays] Move or Recreate

I'm thinking of switching a couple of the VPS servers I have, where I'm running both relays and bridges.  (On separate VPSs, obviously).

I know how to maintain the keys for both relays and bridges for the replacements, but was wondering exactly what does that buy me, as both will now be running at different IPv4/6 addresses.

As opposed to just blowing away the current ones and starting fresh copies.

Cheers.