My understanding is, the German 88 was the best gun of the time, bar none. It was versatile, ubiquitous, and kicked serious ass.
It's real strength was the Wehrmacht's doctrinal flexibility in using it. They were willing and able to use it in its original AA role, as an AT weapon (though due to its height, North Africa and the Russian steppe made what would normally be a handicap a virture) and as general-purpose artillery. The Brit 3.7 and US 90 mm AA guns were ballistically similar but just were never used for anything but AA purposes.
Talking about "The German 88" is kind of like talking about "The American 75" because for the 88 there were a wide variety of different mountings and even two completely incompatible chamberings that share only a bore diameter. The 88L56 on the Tiger I was a less-powerful cousing of the 88L71 used on the Tiger II, the latter used a considerably larger, higher-capacity cartridge case.
