I have a couple of observations about the U48:
1. It came much later than the pioneering U47. The reputation of the superiority of the U47 vs. the ribbon and dynamic mics, which were common in the US in recording studios at the time, had been established.
2. The U48 with its almost military-looking matte gray paint was not quite as appealing when it came out, compared to the original U47 with its chrome top, and its long, well proportioned body dimensions.
3. The s/n and dynamic behavior is a tiny bit worse in the U48, because, in order to squeeze out double the center electrode's polarization voltage for the rear in figure eight, the total available 105VDC from the power supply only translates to 50VDC for the mic in cardioid (60V in the U47.)
I.e. the slight loss in polarization voltage, and therefore a slightly worse s/n and altered dynamic behavior of the U48 is audible, but by no means all that objectionable (that deficiency, by the way, can be remedied.)