In the case of long-term venous access (or presumably intended for use for more than 4-6 months), the fundamental criteria for choosing the most appropriate system lies in the frequency with which the system will be used.
A frequent use of venous access (more than once a week, for example every day or every other day) yields a preferential indication to an external system.
An infrequent use of venous access (less than once a week, for example every two or three weeks) places a preferential indication on a totally implanted system (port).