I own both. German is stock V1 and my US made has GGI work done on it but there is absolutely no difference in reliability between the two. Granted I didn't do a Todd G. test but I haven't seem one hiccup in either of them. The only difference I noticed is the "HK45C" that is engraved on the slide is engraved deeper on my German slide than my American slide... My American made one seems a littler lighter too but I think that's due to the LEM and the GGI work more than actual mechinical differences.
If you need a push to get it consider this... Todd G used a American HK45.