Analysing mp3 quality with spectrum, how to interpret the results?
At those relatively high rates, the possibility (for a human) to hear a difference depends a lot on the device it is played on. My first suggestion would be to rely on a panel of testers (possibly bats, for the high frequencies), use the best audio system you can, and compute a Mean Opinion Score.

I do agree that the frequency limitation around 20 kHz might seem in disadvantage of the second image, but as you said, low-freq bits can then be better allocated (possibly some).

Similarly as @Marcus Müller, I suspect the high-freq band in the first to be spurious. Especially since it really looks symmetric in the time-frequency plane (modulo the contamination with the real audio), and the aliasing hypothesis sounds nice here. 

As said in a comment, you can subtract one decompressed sound from the other. Hopefully, by a careful listening, you could check whether the difference is meaningful, or not.

So, I'll, too,  go for the second for the best.