The new LG V40 looks similar to the V30 last year, only with more cameras. That means a premium metal and glass design, water-resistance, rear-mounted fingerprint scanner, wireless charging and no removal battery. The same thing goes for the Galaxy Note 9. It's a sandwich of metal and glass like every phone over the last few years. The front is all screen, the back is all glass, and everything neatly blends together and feels great.
Both of these phones offer huge screens, powerful cameras, and are covered in glass on the front and the back. They both have wireless charging, they're both water-resistant. The design is similar yet different enough that it's all about personal preference.
One thing to keep in mind is the big squared edges of the Note 9, compared to the rounded corners and slightly smaller frame on the LG V40. If you want the giant screen but have small hands, the V40 is probably the better choice for you.