My opinion would be an ambiguous "that depends..". If you have a number of operations going on aside from the SNMP operations that do not depend on the SNMP operations I would imagine asynchronicity might give you some performance improvements, assuming of course you have available resources.
Of course there are things to consider before going down this road, the scope of variables, file handles, etc come to mind. The Async or Proc::Fork documentation might give you an idea of what problems you may encounter.
It might help to be a little more specific about what you are doing now and what you would like to accomplish