Is this a myth like frame stiffness? I'm debating between getting mountain style shoes and road shoes. Sometimes I do ride on dirt trails so the traction on the ground would be appreciated.

Any opinions appreciated

You can get pretty damn stiff mtn bike shoes if youre worried about it.

What if I were Romeo in black jean, what if I were Heathcliff....

Do you really think that there's significant hysteresis in the soles of your shoes or feet? "Efficiency" is a totally bogus reason to wear stiff shoes. You're not losing power because your soles are flexing.

Still, there are lots of good reason to prefer stiff shoes. It's a lot more comfortable for most people. The force from pedaling is spread out over more of the shoe, which makes your feet happier. Your feet don't move around as much and they don't rub around in the shoe and create hot spots and blisters. That probably helps you go faster. And for a lot of folks, stiff shoes just feel a lot better.

And yes, you can get very stiff MTB shoes. As a general rule, the more expensive the shoe (within one make), the stiffer it will be.

Can someone flame me in a useful way, thanks grolby

Frame stiffness is not a myth. Some frames are stiff. Some are not so stiff. No myth.

...oh you meant with respect to power transfer....hey, look! Didn't Armstong just fart or something otherwise news worthy?

Stiffer soles are usually carbon fiber, and they are usually also lighter and also tend to be included in better shoes. So, I would suggest that lighter shoes are typically better and faster for a variety of reasons.

You can get most premium shoes in nearly identical versions for road or MTB. A personal anecdote about shoe stiffness and it's effects:

My Sidi 5 mega shoes were just that: one set of road and one mtb. I couldn't tell any difference while wearing them. None. Speedplay Zero on one and Shimano on the other.

But the plastic soles started to breakdown with use. I'd get off the bike and hobble with a severe limp. Could barely make it up stairs. The sole was going soft and I was causing serious strain on all the connective tissue in my legs trying to stabilize my foot while mashing away. A new set of uber delightful and stiff CF soled shoes immediately cleared up the issue with no other changes.

Soul stiffness is not a myth.

I was using a set of Carnac Ellipse shoes for about 7 or 8 years. I loved the fit, and I was reluctant to give them up. I was also using Speedplay pedals at the time, and my feet would bother me on longer rides (about 70 miles and up). I distinctly remember one ride where I was in agony every time the road tilted up even slightly, because it meant more pressure on my aching feet.

When I switched to a pair of Shimano shoes with carbon soles, my comfort on long rides improved substantially. My old Carnacs had gradually gotten softer over the years, and I didn't notice the change day to day. However when compared to a new pair of shoes, the difference was night and day. I think that for longer rides, or ones with a lot of climbing or sprinting, you'll probably benefit from the stiffer soles, especially if you use a small platform pedal.

The thing about using mountain bike shoes is that the bike pedals which accommodate them tend to be heavier than their counterparts for the road, which can be annoying to weight-weenies - Egg Beater pedals being one of the exceptions. You can certainly purchase reasonably priced mt. bike shoes which are quite stiff.

I already have crank brother candy c pedals