Need Advice Please

[skipdogchip]

I am in the market for a keyboard for my four year old daughter.  I have narrowed my search to a Yamaha YGP625 and the Yamaha YGP525.  However, I would like to know the difference between a "lightly weighted" and the "graded hammer system" features of these two selections.  Does the 525 have the "almost true" feel of an acoustic piano?  I saw and heard the 625 at a local dealer and WOW I was impressed.  Is the 525's key feel as impressive as its counterpart?
Thanks for the help and any advice you can pass along to me,
Skippy