If there are multiple contacts on a deal (which is quite often the case) I’d want to include all of the contact details in the internal email.
Our email subject would ideally be:
Company | Deal name | Deal ammount
Our email description would be just about every other property:
Deal name (again)
Deal description
Deal amount (again)
Deal company (again)
Deal contacts (probably a comma separated list of the contact names)
Deal owner
Deal closed won reason
Deal URL
In terms of priorities between company and contact details, I think the company associated with the Deal is the most useful. Having the contact details is a nice to have.