The bars are plated, not an alloy, the gold bars will be gold plated. Really, the plating is just to stop the tarnish of the copper metal and to give a little bling.
More important is the design of the bar. I always liked the Much-More standard bar - but when I switched to the Much-More premium bar I had issues with the bars pulling off the solder joint in off-road racing - because the bar is much stiffer than the solder joint. Stepped bars won't damage the heatshrink, but I have had to use flat bars for my B4 buggy because the battery tray is too narrow for the stepped bars to fit.
So to sum up - any stepped bar in a dogbone shape should be fine for 99% of applications. Silver or gold plating, depending on your taste.