Unlimited is significantly much more. A non popular mirror 1st edition is $2 but the unlimited is $30. Japanese sellers recently caught on that unlimited is much more valuable. A few years ago you could find unlimited in random listings without a premium being added.
Not trying to be a downer, but I don’t recommend doing unlimited if you are just looking to complete the sets. It will be very expensive to complete, which likely would take several years if not decades to do. You are competing against species collectors checking 3 times a day for new listings, and also some set collectors who are halfway done already. It’s not fun seeing Umbreon mirror for $2k when the 1st edition is $20