There can’t be any 100% sensible reply to the original question, which is “which drive do I trust”, for two reasons:
PIE/PIF plots are not an analysis of errors on a disc, but a result of the reading process. All drives will report different errors. That’s for the theory. Call me nitpicky, but I think it’s important to constantly fight the idea that some drives would accurately “analyse” discs while others would inaccurately “analyse” them. What’s reported is always a [I]combination[/I] (+ possible chipset peculiarities, which is incidentatlly the case with NEC drives).
3540A scanning behaviour…?
Before buying my own first unit, I’ve been asking about the scanning behaviour of these drives. I’ve been told “maybe you’ll get lucky, some units are good (consistent) scanners and some others are erratic”. [B]So maybe you have one of these “erratic” units[/B]. But out of just a handful of scans, it’s impossible to tell.
Now to some considerations from my personal experience (+/- 400 scans performed in two 3540 units) and the time I’ve spent browsing the NEC forum for 3540A scans:
My first unit was so consistent a scanner that I bought a second one. These are my main scanning drives, and about one year later I have yet to find a reason to complaint about what they tell me about my discs. I CAN trust my 3540A scans to predict the behaviour of my discs in my different drives. I can’t say the same about my Benq scans.
But scanning with a 3540A implies to take an important point into account:
Chipset peculiarity! These 3540A drives (like most, if not all NEC drives) can report impossible PIE levels (over 1664) thus they don’t report PIE in a way that is compatible with ECMA recommendations (under 280 PIE). This is accompanied with a dramatic magnifying effect on PIE variation, which I personally find extremely useful when using scanning to check for the degradation rate of my discs. But it introduces a “difficulty” when reading the scans: one has to adjust the “standards” accordingly, meaning relaxing the 280 PIE limit. I consider anything under 500 as OK, anything under 150 as good, and anything under 80 as excellent. For PIF, though, the standard rules still apply.
Nevertheless, I’m gonna conclude by saying that in your case, you’d probably be better off by scanning in your LiteOn drive…