In the case of VAD presumably intended for use for more than 4-6 months (long-term venous access), the main issue in the choice of VAD will be the expected frequency of use.
A long-term VAD to be used frequently (more than once a week, for example every day or every other day) should preferably be an external catheter. On the other hand, if the use is infrequent (less than once a week, for example every two or three weeks) a totally implanted VAD (port) should be preferred.