Originally Posted by dabac

When it comes to bikes, chains are a bit like religion. Some people believe in this, some believe in that, others don't care much either way. Some have sampled several different varieties, other remain faithful to one brand. Some are willing to go on crusades to get others to see the light, others are quite content with whatever works.

Personally, I find that correct assembly, frequency of care and lube, followed by ride conditions are much more important than chain brand.

Shimano / SRAM are two different companies. They both make a range of products, from high-end to fairly basic stuff. Compare the same level, and you'd need to look quite hard to spot much of an everyday advantage to either of them.

HG40 vs HG50 isn't much of a difference. Functionally they're supposed to be interchangeable.
Might be that HG50 is shiny, plated with something-or-another(chrome? Nickel?) as rustproofing and bling points while the other may be left black. Shiman does that for cassettes anyhow.