Depends on what you're looking for:
If you are only looking for a unique in that one area, then yes you should restart. Only one achievement unique can spawn in a zone per game (as far as I know), so it doesn't make sense to keep looking for them in that zone.
If you are looking for uniques in multiple zones, then once you find one in a zone, leave that zone and move on to the next one.
Edit: It seems I misread the question... oops
Either way, what I said remains. To answer the question, No. Rares and Uniques are independent.
Edited by Indoor#1963 on 3/3/2013 12:40 PM PST
Rares, champions, and uniques can all exist on the same map. There is the question on whether or not uniques occupy the space of one elite. If they do, then maps that spawn only one elite you will want to reset. Another question is whether or not 2 uniques can spawn on the same map.
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