We prefer Regent if we are going from USA to asia/australia. The business class up grade for Oceania is much more. (included on Regent)
In many other areas, such as South America, Regent's included (I do not like "free") shore excursions are a good value compared to the limited Oceania.
For other cruises, such as Caribbean, all things considered, Oceania food is better. Regent food is very good. No complaints.
However, several meals at Oceania are MEMORABLE. The sea bass at Red Ginger. The scallops gnocchi at Jacques. The pea vichyssoise at Jacques (where i first understood "depth of flavor") make us reconsidering Oceania.