Here is an old comparison chart. Perhaps some people have gotten good Pony data, but I haven't (by good I mean Foresights and Backsights that match within a reasonable limit. And even the Disto X - with a fresh calibration - does not always produce FS/BS errors of a degree or less. (But the next time the same Disto X is calibrated it may produce FS/BS errors within a degree). However, the Disto X rarely exceeds a 2 degree FS/BS errors (with a fresh calibration). I can't say that for the Pony. 8 degrees has not be uncommon in my experience.
This chart is a comparison to Theodolite data with a plot of the Az and El errors. Some of the Pony data is off the scale.
The DUSI with the Beta software did well, but the DUSI v2 has not lived up to that promise (at least in my testing).
I'm not comfortable recommending anything other than the Disto X at this point. And all indications I have is that they need calibrated (and I have worked with 4 of them) at least once a month. The fact that the Disto X is first a Disto has some disadvantages to the DUSI and Pony. Unless Phil has improved the algorithm the Pony uses (like going to the Disto X / DUSI method) I think it will be limited. And Unless Sean sorts out what is wrong with the DUSIv2 software, it is also limited.
I like the Disto X - but it can be frustrating at times. I have gotten what appears to be a good (or even great) calibration (based on the calibration output), produce a tight grouping in a plot like above and yet fail the compass test course basic FS/BS test. One day I calibrated 4 Disto Xs and only one passed the test. Very annoying.
I recently tried demagnetizing batteries as one poster here claimed the cause of Disto X's going out of calibration was dominated by change in the batteries magnetic properties as they discharge - and if you demagnetized before each trip you could avoid a recalibration. I used the DUSI gaussmeter to check the field to verify the batteries were demagnetized. I was using a commercial demagnetizer and found that quite often it took a very large number of attempts to actually get some batteries demagnetized (while some only took one try). I was using lithium anyway because of they don't change as much as they discharge. The original advocate of demagnetizing the batteries didn't say how he verified that his batteries really were demagnetized. He was using regular batteries, not the lithium ones, so maybe his batteries were easier to demagnetize. I haven't had a chance to get the data to prove / or disprove this theory.