Basically arbiter design should depend on network complexity and topology.
If Your target is a small network with a fixed number of end points (rather small traffic rate), I would recommend fixed-prio arbiter module where the processing queue is based on hoop-count (number of nodes passed) and a simple FIFO register for packets of equal priority.
Round robin is more complex in terms of implementation (time sharing between packets of the same importance) and targets larger networks with higher traffic rates.