What are the advantages/disadvantages of using 3 vs 4 actuators for a 3 dof motion system?

[helios1234]

What are the advantages/disadvantages of using 3 vs 4 actuators for a 3 dof system? By three dof I mean the roll/pitch/heave. If weight is not a concern would 3 be more than sufficient and achieve the same results?
Thankyou!