We have been wearing triathlon shoes for as long as we could remember each other cycling. Recently, we bought a pair of cycling shoes each.
Esther swapped out her Specialised triathlon shoes for a pair of F:zik road cycling shoes. Wee San swapped out her Shimano triathlon shoes for a pair of S-Works road cycling shoes.
Here's our amateur reviews / personal opinions:
1. Triathlon shoes are roomier than the road cycling shoes. To fit the quick transition from swim to bike.
2. Coming out from swim, triathletes feet are often wet. Hence, triathlon shoes often come with mesh top layer, while cycling shoes have top layer made of sturdier material.
3. There is also better ventilation from the mesh found on the triathlon shoes. We can't say that there is none on a cycling shoes but comparatively lesser.
4. Quick transitions, wet feet also mean triathletes often wear the cycling shoes without socks. Triathlon shoes are often made of seamless materials. Road cycling shoes are less so, as roadies tend to wear socks with the road cycling shoes.
5. Triathlon cycling shoes often only have a velcro strap, whilst road cycling shoes use ratchets, or buckles or a combination. A single or occasionally double velcro straps used for triathlon shoes because triathletes often leave their cycling shoes on the pedals and put on the shoes via a fly mount. Can't do the same with road shoes, lest you end up a flying pig! :)
6. Heel tabs on the triathlon shoes also help with the quick transitions and flying mount. However, these are absent from road cycling shoes.
So which is better? We think with proper fit, good techniques, both types of shoes are used for different purposes. Triathlon shoes are good for cycling up to say, a half ironman distance. And we feel for distances above that, road cycling shoes with the narrower fit, sturdier feel provide better power transfer to the pedals.... as proven by Esther dropping the guys on the ride like flies! :)