I'm just back from a trip on Ventura and thought I would give my thoughts on the differences between Cunard and P&O
Breakfast
The menu selection is smaller than on Cunard but all the food was good. Unlike on Cunard they take the juice order at the same time as your main order. One very big plus for P&O is that the toast comes in a toast rack, which gives lovely crispy toast.
Lunch
Again a smaller selection than on Cunard but everything I had was good.
Dinner
There were many items that appeared on the menu everyday so the choice was limited, but all very good.
The wine list was on two sides of a sheet of card, not the large folder you get on Cunard.
Bars
The selection of drinks was very limited with very few choice of cocktails or spirits.
Ventura has a good selection of venues with entertainment on in each, but not as much live music as on Cunard.
Afternoon tea was only available in the buffet and was self service with quite a queue.
There is no selection of hot food on the breakfast room service menu. There is a charge for the other items on the room service menu.
Fruit juice is only available for free at breakfast, any other time you have to pay for it.
You cannot get food in the pub, but there are four choices of where you can dine and pay extra.
The entertainment was pretty much the same as on Cunard although maybe aimed at a younger audience.
The passengers were younger than on Cunard, although I don't know if that is normal or due to the ship going to Amsterdam.
All in all I enjoyed the trip, but I will not be rushing back to P&O, but that's not to say I wouldn't sail with them again in future.