About to do just that. But why is a solid case back preferable?
Boss has already answered briefly above, I will just give a little clarification:
From the front, PAM915 and PAM914 HWF are generally equal, both with advantages and disadvantages (first of all, the sandwich has unnecessarily wide cutouts in both cases).
The releases did not take place at the same time, and I admit differences in the shade of lume and fonts, but even without a parallel comparison, I am sure that they differ from each other no more clearly than any differs from gen (there are always differences in shades from gen, in the case of patinated lume and beige fonts, in fact, on any model).
The cases are most likely generic and of course they don't meet the specifications of the P.5000 cases because PANERAI made them thinner and in a slightly different geometry, while HWF uses one case for the bettarini models, be it OP.I/ II/X/XI or P.5000 or P.6000 (Although for gen, the models of which this factory repeats, these are at least 4 different types of cases, not to mention the specification of specific models).
Yes, by the way, the crystal is also identical, and in all cases it has distortions, unlike the gen manufactory models.
So, besides personal taste (with and without a second hand), there remains a rear view, i.e., the execution of movement and caseback.
The situation is such that both PAM914 and PAM915 were produced both with a transparent caseback and solid, however, the transparent one was only in the first production series (V), and in the subsequent ones there were only solid.
Here it is necessary to make a reservation that engravings (As recently done by both HWF and TTF) are not correct in both cases. On the transparent case number is not correct (7060 - which they engrave on many models, generally belongs to the case from carbotech, instead of the correct 7080), however, the solid caseback PAM914 has a completely inappropriate N series (2011), while this model began to be produced in 2019 (V series), so we remove the engravings from the comparison equation.
Ultimately, the overall look remains, and of course the P.5000 has a much smaller balance wheel, and in a different position, than the 6497 that HWF uses, not to mention the decorative plate and its quality. While a solid caseback, albeit with an unidentified number, is protected by visual protection, even if from 6497 it does not even have decorations, which, under favorable circumstances, no one, even you, will see.
For all of the above, I would prefer the PAM914.
I hope I was able to explain my remark.