My experience:
Alzan - 3/4 Upjohn
Upjohn - full strengh
Xanor - full strength if fresh (sometimes are mushy from transit)
Trankizam = Upjohn strength
Zopax - close to upjohn, but not quite as strong. 1/2 - 3/4 strength. varies
Gador (2mg bars) = haven't tried yet, will soon.