The difference of subdivision surface modifier between 2.7x & 2.80? This is a plane with 1 level subdivision surface modifier, it seems that version 2.80 using a new method to subdivide and smooth the mesh. This is almostly different from the version 2.7x and other 3D softwares. Why the developers make this change? Is there any advantages of the new method?
Yes, 2.8 now uses Pixars OpenSubdiv. So there is a change on how they are computed and behave.

[EDIT]
I actually can't see why there should be a difference here from maya for instance. You may want to discuss this on devtalk.blender.org.