My experience with oils has been the big advantage that oils have over watercolours
in that they can be worked on many times to achieve the desired result. This means
that the location painting can be finished off in the studio.
When painting with oils outdoors I use a drying medium that enables the painting
to be touch dry in a matter of hours, this is a big asset when traveling to a number
of locations. Weather conditions are more containable with oils than watercolours,
particularly in damp or wet weather.