What made the T-1000 terrifying, aside from the morphing arm blades, was that it was a more direct mockery of a human being. A human is a mind/spirit in a body mostly comprised of water. A T-1000 is a computer program in a liquid metal body. The T-800 is a machine wearing a human skin, but it fails in becoming uncanny. It is a blunt instrument, a disposable tool, and while it relentlessly and ruthlessly pursues a target, it only intends to kill you and nothing beyond that. The T-1000, however, is a testament to Skynet's ultimate goal; to supplant and *replace* humanity.
It's always funny seeing non CGI in a movie that's such a CGI flex, like when they use twins and such. I guess using physical objects was easier to film from different angles and keep consistency.
