That's not really enough info to answer the question properly. However, at face value, the 8500 memory would most likely be the better of the 2. If you slowed it to the 7200 speed it will likely run the same latencies as the 7200. However, there is less chance comparitively that the 7200 will run at PC8500 speeds.
But, other factors play into it all so PC8500 may not be "better", especially if you are not going to OC.