I like that Oceania‘s pricing is à la cart. That way I can pay for what is important to me, and DIY other aspects. For example, I can bring on board bottles of wine and only pay a $25 corkage fee in a restaurant. There’s no fee if I consume it in my cabin. At happy hour I can get a cocktail (double) for the price of one. When I have an unlimited beverage package, I probably drink more than is good for my waist line. So, I like being able to consume alcohol without having an unlimited enticement.
I have heard that Viking does good shore excursions. Depending on the area visited, I might prefer to join in a private group excursion; more customized and more personalized instead of paying for it in the cruise price. It all depends on your preferences.
One thing Oceania does so much better than Viking, is the cuisine. Everything I read tells me this is true. O’s food is much better than Viking’s. For this statement, I rely wholly on the vast majority of opinions I have read on cruise critic; I have never cruised on Viking myself. Enjoy your cruise!