thanks for providing the test results and technical information,
@Laurens and
@Medved and
@RRK - very helpful in gauging the performance and efficiency of the Qianshun ballast.
so far, i am still
VERY impressed with the 35W one i purchased.

i ran it for 12 hours yesterday and it was just barely warm to the touch afterwards. i also had a couple of voltage sags when my air conditioner started, enough to cause all my lamps to dim or flicker for a short amount of time, and the ballast re-struck the lamp instantly as expected, no "complaints" or issues.
i'll see how it holds up over time, and i have a Qianshun 18W SOX-E ballast arriving at my home tomorrow afternoon so i am looking forward to testing that one out as well.
assuming all is well with these ballasts over time, i will in the future consider a high recommendation of these ballasts to those of us looking for new, efficient gear to keep our SOX lamps running happily.
BTW - the magnetic ballast i have been comparing against is an Advance 71A0490 (photo attached). i have 5 of them and have been swapping between them for control purposes - all behave pretty much identically as they all have the same date code and were in more-or-less daily service at my workplace for the same amount of time (about 12 years). i've replaced the 14uF capacitors on 2 of them to bring them back within spec; the other 3 are doing fine. this ballast choice could explain why mine have higher losses - they're dual-purpose ballasts that can also run 55W lamps, so i imagine some compromises in efficiency were made to allow them to run both lamps.