Voltage has nothing to do with the workload, just the hardware's stability. In general, the higher the voltage at a given frequency, the more stable it'll be (until heat or junction breakdowns become an issue).
The amount of work done is proportional to the operating frequency. I see about WU 1.53/MHz with a 2-chip stick, so 225MHz should run about 344 - plus or minus, because USB traffic and pool latency and whatever.
And that's what I am seeing now, OK thanks for the confirmation! Ok I'll Bump them back up to 250Mhz, And return the voltage to 1.4 as that seemed to be running fine. I just wanted to see if the 2pacs would be more efficient or stable at the lower clock with higher volt.