I'm not familiar with Fresenius, but I CAN tell you about NxStage. The machine is relatively small and portable. We were able to pack it up and travel whenever we wanted. We even took it camping with us for a week in Florida. And went to Massachusetts to visit our daughter 4 times a year. NxStage would send the supplies ahead with no problems.
Many people fly with NxStage and that CAN be more difficult, but some prior planning and communication with the airlines goes a long way.
Tech support for NxStage was always very helpful. They patiently walked us through several doozies of problems (mostly user errors). When we DID need to have a machine switched out, the new machine arrived the very next day.
I hope some others weigh in.
Aleta