The newer roof sections, going back at least to 3666 fit together slightly differently.
The originals have a triangular piece with a hole for an opposing peg to fit into. The peg is still there on the newer ones but the triangle has been reduced so that the hole is now a curve in the surface of what was the triangle.
Those longer supports on the 2x1 floors doubled as decoration so it's a shame they had to go. Then again, the amount of broken ones I've seen I can understand another reason why they are no longer a design feature.
I suspect the only parts not to have changed are the wooden rails and the breads. Possibly the doors and gate doors too, err and maybe the bar across the gate and the supports for that and probably the roof connectors and the stepped roof end.
The newer walls click together, those bumps aren't just to make the tabs thicker, they click together. The rails on the originals are higher and have squared edges whereas the newer ones are tapered at the front.
They changed the crenellations including redoing the gate with the new style, but the old style is still seen in the stepped roof end on either side. Speaking of which, I'm surprised they never made a window pane or cover to fit into the window of that piece.
One thing I've noticed, and this is not really steck, is that the new well doesn't fit the wooden frame very well. I've had a few of them now and they all had excess plastic in the grey stone part which I had to remove with a small chisel to seat the wood frame properly. As is it's impossible to get one side of the frame flush with the well.
Did the original steck only apply to the castle parts?
One last observation, why are the new bottleglass windows dark instead of being clear?
