Hi Liz,
I agree with both, you and Markus. However if you follow system copy method then you have an advantage of upgrading the database from 10g to 11g in one go (less downtime for current/'source' system, too) along with the 'clean' data move advantage, as Markus suggested.
You may like to try inplace windows upgrade for one system first (normally sandbox) and see if everything is good. I see this in-place upgrade note for the first time.
Thanks
Dev