Steyr
154
From my limited knowledge and experience with both brass and german silver :
German silver is slightly more expensive from brass. About 10-15% more. Did't check myself but from a conversation with my boss couple of years ago.
German silver costs more in machining. The Nickel it contains requires to change tools more frequently. Some manufacturer simply refused to work with german silver. Now that lead is forbidden in brass, the difference is getting smaller and some third part makers are now accepting to proceed with german silver.
German silver is better on a mechanical point of view. More rigid, you can make slimmer design. Thread are more resistant. Less prone to scratchs...
Being harder, german silver allows better finishing. But takes longer and therefore $$.
Brass is more prone to oxydation and it does not react well giving spots and unpleasant shades. Therefore, you have to plate it. Rhodium is rather common, with intermediate layers. Plating is a polluting treatment, even if environmental laws are getting more and more restrictive. Another problem with plating is that if you scratch the finished part, the part is dead. With natural german silver, you could still redo the finishing.
As for the yellowish, german silver takes a yellow coloration over time from oxydation. That taint can be washed out very easily during maintenance (same with brass actually when not plated). It appears some german silver are more yellowish than others. I'd say Lange's alloy looks more yellow than the one I usually see. Don't have any explanation here. Could be more oxydized but don't think it is the only reason. The yellow color may also vary over decades. I guess the alloys composition changed. I remember from a jewelry exhibition where some old prototypes made out of german silver were displayed, the material was looking very ~white~. Same with fine old pocket watches.
So, to me there is no reason to go for brass except for lower costs.