In VERY broad general terms from what I have gathered/seen is West Germans tend to be more "sport" driven while the dogs from behind the old iron curtain tend to be more "serious working". There are exceptions of course but that is the most basic "nutshell" difference.
Like with any other "flavor" of GSD there are varying degrees of drive/temperament/nerve between different lines and individual dogs.
There are too many exceptions, too much cross breeding between the lines to say one type is this and one type is like that. I am not even sure I would say the DDR/Eastern block dogs mature later. My West lines show mental maturity usually around 4. Some lines may be ready to trial earlier, but it doesn't mean they are mature.
I know too many WG dogs that are very serious in the work to claim that the EB dogs are more serious. I have seen too many EB dogs (Czech lines, not so much DDR) that are highly driven for toys to say that the WG lines are more toy driven. The EB dogs do, in general, have bigger heads and more bone.