I have migrated several production EBS instances to Exadata. (you can read my Exadata migration stories in my blog ->
https://ermanarslan.blogspot.com , just search by the keyword Exadata and you will find lots of articles)
I have experienced that EBS 11i/or R12 accelerated with the Exadata transition.. (this was the case in my projects)
You can also read my Exadata reviews on ITCentral Station;
https://www.itcentralstation.com/product_reviews/oracle-exadata-review-44119-by-ermanarslan-oracle-acehttps://www.itcentralstation.com/product_reviews/oracle-exadata-cloud-at-customer-review-70323-by-ermanarslan-oracle-aceEBS performs quite well on Exadata..
When it comes to oracle database, Exadata is the best platform for performance.
Of course, sometimes exadata aware-tuning may be required.
The answer to these questions depends on the exadata version as well..
For example Exadata X8M is a very very fast, high end machine.
Why don't you make a POC?
I suggest you to do a POC and check your performance.
Make a list of all your reports, queries, critical forms.
Run them on Exadata and make a comparison.
But in the end, I think, most likely EBS 11i will run faster in Exadata.