Frame is newer, in production, and requires less hardware setup. It’s capable of wireless use and some games can run without an additional gaming PC. I believe the display is higher resolution as well.

The Index is cheaper but AFAIK is no longer in production. It requires base stations to be setup to track the headset and any controllers. A cabled connection to a gaming PC is required.

The Frame’s price and separate bundles are a flawed delivery, somewhat understandable due to the market conditions, but it’s one of the better VR options on the market as a whole.