Disparity in Hash Rate between 2 L3+ miners

I have 2 L3+ machines that have always run pretty much the same in terms of how they perform.
The 2 Live worker status windows at top left of the Earnings page will now show the top rig at a noticably lower hash rate than the one below.
This with all other matters being the same on the l3+ System config, and even tried with the top one overclocked.
So as an example on the Antminer Login status page I'll show the top unit now at 508 MH/s average and the bottom one at 500 MH/s average, the hash rate as shown on Prohashing live worker status on the top rig will be noticably lower whether left at stock speed of 384 or slightly overclocked. That is the rig actually hashing faster in this case will show up slower on the network, and if put back at stock setting, even slower even thought both antminers would show 500 MS/s in their own status readout.
What is this about?

why bother, no one cares.

Ziggy,

I'm a newbie on the site too and had a couple of follow up questions on L3 hashrates.

1. When I use litecoinpool for mining, my hashrate as shown on their site was about 1/2% less than what the Antiminer said that I was generating. On prohashing, the site hashrate is typically about 3% less. Is that normal or are there adjustments that I should be making? I have tried changing the difficulty, but in an hour or so, it always ends up in the same general hashrate range.

2. Similarly, my impression has been that attempting to maximize the WU's was more important than maximizing the hashrate as shown on my end. Is that true?

Thanks,

Mike