As far as the quality of the makeover, there really wouldn't be any difference.
BUT.....my girls did this at the Castle and I have to say that walking down Main Street heading to the Photo Studio was probably THE best time they had with their makeover, lol. People would stop and point at them, they even had several people taking their photos, including an Asian group that asked to pose with them! The Photopass photographers (3 different ones) stopped them and asked to take their photos, and did a LOT more than just posing them with the castle behind them. One of the photographers took them to several Main Street buildings and posed them in front of these buildings.
All in all, the girls have often said they felt like "movie stars" walking down Main Street that morning.
After getting their photos done we needed to get to GF for afternoon tea....stopped at the boat and asked the driver if his boat went to GF and his response was "if that is where the Princesses need to go, that is where I will go". They felt like true royalty (and I didn't bother to point out he was going there anyway).
That evening we went back to Main Street and the walk towards the Castle again had a lot of folks pointing and lots of compliments (though not quite the same photo ops, lol).
If you have the chance to do it at the Castle, I'd highly recommend it. If your preferred time or touring plan don't make that possible, DTD will also do a wonderful makeover of your daughter. I just think the perks of the Castle and Main Street will always make that one my preference.