As I perused chains I noticed that they seemed to be broken into a mountain bike and a road bike category. Why would they differ?

For 9spd the Ultegra/XT/Saint chains are the same. The box is labelled with all three (HG93). I don't see a reason why they would differ for 10 speed and not for 9 speed, so I reckon it's just marketing. I'm no expert though, perhaps they pushed the boundaries on maximum torque capacity a bit for the road gear?

Sure there's a difference, the box...

I always recommend the cheapest chain with a master link for cleaning. Every thing else is just marketing hype(BS).

10 speed 2x10 Shimano (CN-5701,CN-6701, & CN-7901)are directional, https://techdocs.shimano.com/media/te...9830688497.pdf 3x10 aren't, neither are brands like SRAM, KMC, Connex etc.

Not so much Road vs MTB, but 2x10 vs 3x10. 11 speed has gone back to non-directional (symmetrical) chains

True and even Shimano can't explain WHY those 2x10 chains are limited to double cranks and won't work properly on triples. I've heard reports that they do indeed work with a triple.

Been trying to find the explanation for this myself. My guess would be that the drilled side plates of the newer 10sp Shimano chains may get fatigued from the increased chain angle of a triple and possibly crack. But that is just a guess. Shimano would probably never admit to it if true.

The demands on the chain by the operator, may be different.

As mentioned, Shimano make directional and non-directional chains whereas KMC and Sram don't. I've seen so many Shimano chains put on incorrectly, especially no demo bikes at trade shows, because people want the cut outs facing out. Shimano also make Road and MTB specific chains whereas KMC and Sram don't (actually Sram has moved to differentiation for 11 speed, but the Red22 and XX1 chain characteristics seem the same - besides different weight reduction).

At KMC, we've done extensive testing and feel no need for a category specific or directional chain - one chain for all In fact, our newer X10 and X11 series outer plates are asymmetric for shifting reasons but the chains are still non-directional.

Love KMC- reusable links, non-directional, no bs!

As noted above, the directional design has been dropped by Shimano for their 11-speed chains and was probably an unnecessary refinement for 10-speed. Their older non-directional 10-speed chains (6600 and 5600) worked fine and are recommended for both double and triple cranks.

BTW, doesn't KMC actually manufacture some of Shimano's chains?

+1. Plus, I like it when company reps show up here to actually talk to us.

Agree! So far the KMC rep and the Retroshift guy have posted here recently. I recall Richard Sachs was here a while ago. Any other factory reps I missed?

There used to be regular posts from a Schwalbe rep. Haven't seen him in here for a while. Brooks was represented here for a while as well.

OP here - A truly definitive response. Thank you. The only chains I have used are Shimano (Ultegra and Dura-Ace - with KMC master links) and KMC (chosen after research), usually based on price. Sometimes the Shimano chains can be found at a steep discount, especially after Shimano moves to a new generation.

Thank you for the response. Let me know if you need any chains tested.

Thanks for your support of KMC and Shimano who we've been working together with for over 27 years

Thank you for participating in these forums. By the way, I just purchased a KMC X10.93 chain for my road bike.

Cheers