The a7ii has an integrated stabilizer
The a7 does suffer from sensor reflections, the a7ii does not
The a7ii has a more ergonomic grip but it is also significantly heavier
The a7ii has mount made of metal, the a7’s mount is partially made of plastics which caused some issues.
The a7ii offers improved AF performance, it even works qite well with some adapted Canon EF lenses
The a7ii has a more ergonomic shutter release
The a7ii offers a better video codec
The a7ii is about $600 more expensive
You can consider more detail at https://phillipreeve.net/blog/sony-a7ii-vs-sony-a7/ to comapre 2 of them.