I came across info saying it was the only night fighter capable of facing the DH Mosquito on equal terms, based on speed, manoeuvrability and firepower...but nothing about it being the best nightfighter of WWII.

Hi, you've partly answered your own comment by stating the Uhu could catch the Mosquito. Limited production ultimately never helped the Uhu's reputation, but consider: 1). The results of its first outing in the hands of an expert like Werner Streib. 2). The devastating firepower carried by the Uhu.
If sufficient He-219s had replaced the Bf-110 in time, the results would undoubtedly have been greater. Reading up on whatever is available online, the Uhu was a victim of political battles.