I would say it depends on use and configuration. In the following pic, the double cabinets look good with doors opening to the outside, and the single cabinet on the end opens conveniently to the right. Sorry for such a blurry image.

In the next pic, the door between the sink and range opens to the left, convenient if there are items for cooking stored in it--spices, oils, etc.--but not so convenient for dishes, if that's a clean-up sink.
In the following pic, the cabinet on the far right opens to the left, which seems inconvenient to me, because all the work areas seem to be to the left. The contents of the cabinet should be more easily accessed from the left side, but it depends on what is stored there, which we don't know. Maybe that's a baking counter, and baking staples are kept in the cabinet.
If your base cabinets also have doors, this is a perfect time to upgrade to all drawer bases. GW discussions--all drawer bases

My doubles open in opposite directions in order to give me a full range to put dishes in/out. All my others that are single, open in the direction that gives the easiest access and does not block something.