2 captains flying together can work well..we do it exclusively. We have a 3 captain flight department all with more than 10K hours each. GLEX (Part 91).
Each trip is assigned a "PIC" and that guy is responsible for managing the trip, paperwork, pax liaison, etc. PIC assignment is rotated to the next guy on next trip.
There is no "seniority" and no power trip so CRM is pretty good. We often get compliments from sim instructors on our CRM. We rotate legs and weather, fuel, flight planning is shared equally.
2 equal but highly experienced captains can work well together. Works for us at least but it all comes down to personality. Might be a struggle with the nervous, insecure type....and we all know a few of those.