Is there a difference between the mansion and the hidden mansion?

In Luigi's Mansion, after you defeat the final boss, the "Hidden Mansion" is unlocked. But from the looks of it and the ghosts I am defeating, the hidden mansion is basically the same as the first mansion. Is there any difference between the two?

Solution 1:

Depending on whether you are playing the PAL version of the game or not, different things may change.

Things that change in all versions:

• Ghosts do double damage
• The Poltergust 3000 is 1.5 times as powerful, making it easier to get more money and therefore better frames

Things that change in PAL versions:

• The mansion is mirrored horizontally
• There are more normal ghosts around the mansion
• Bosses are more difficult, having different attacks
• Rooms are much darker (but only as dark as in the NTSC version - normally, the PAL version is brighter)
• Boos often have increased HP, though some have decreased
• Fewer hearts appear
• Speedy Spirits and Gold Mice always give up a Silver Diamond when caught, raising the maximum possible amount of money from 142,390,000G to 186,440,000G
• 45 rather than 40 Boos are required to fight the final boss
• Boos are faster and more difficult to catch
• Five ghosts rather than three appear in The Artist's Studio

To read more in-depth and look through sources, see here.