I would just execute the statement in question 5-10 times while profiling it for duration.
run it 5-10 times without qualified naming and then 5-10 times with qualified names.
average the durations
probably run dbcc freeproccache and dbcc dropcleanbuffers between each execution to standardize the results.
it wont be a perfect test statistically, but you should see some measurable differences....
Gregory A Jackson MBA, CSM