imo:
Trad heavy metal - more blues scales, more pedal-point riffing, more songs about women and music, more mid-tempo; WASP's S/T, Savatage's Sirens thru Power of the Night, earlier Riot, Helstar's Burning Star
USPM - more galloping riffing, more guitar harmony, more songs about fantasy, history, etc, generally more up-tempo; Queensyche's The Warning, Arch-era Fates, Titan Force, Helstar's later 80s albums
But there's still overlap between most of those. On the Panzer front, Symphony of Terror and The Watcher are USPM, while Licensed to Kill, Warfare, Cardiac Attack, Generally Hostile are trad or speed metal.