Yeah, very similar. The main reason is that you can get about 10x more height underground. You can dig about a mile deep. An Energy Vault tower is about 500 feet tall. And as mentioned below in other comments, adding more height gives you more storage per weight, so it's super important. Adding more height and weight scales quadratically while just adding more weight (in side by side towers) only scales linearly.

https://docs.google.com/presentation/d/17FI-jrI9RWS3q7Ng44Yh...