Best way to compare two 3d models?

Hi

I've made two 3d models of a site I've been working on. The purpose of the work is to protect the remains of an iron age settlement from coastal erosion. 

The first is part way through the project: https://sketchfab.com/models/b26c48fa305c48db82bc2348d374c145

The second is at the end of the project: https://sketchfab.com/models/df2d15cff0bd4c34962855f2dc7c6e08

Whats the best way to compare the two models? Is the any way I can overlay one over the other to show the progress? Or can I overlay the maps?

I know this is not strictly a Maps Made Easy issue but any help in pointing me in the right direction of the software I need to be looking at would be very gratefully received. 

Thanks

Ross