Either product will do the job of dechlorinating tap water. I have used both. The problem I have with Stress Coat is you get a false negative reading for ammonia. I was cycling a bank of tanks that I set up in my fish room, added the ammonia to the tanks, gave it a minute, tested and it was negative for ammonia. Thought the test kit might have gone bad, bought a new test kit same results. Did a little experiment with 2 buckets of water with ammonia added to both and Stresscoat added to one and prime to the other. Bucket with SC tested negative for ammonia, bucket with Prime tested positive for ammonia
I would go with Prime
Just thought I would pass on my discovery.