Shimano Parts, Technical Difference
 

I'm curious, how different in technical and performance aspects are these components:
Shimano Sora, Tiagra, 105, Ultegra and Dura Ace?

Sora is a different animal than the rest. The brifters (brake shifters) use thumb levers to downshift. The others use smaller levers just behind the brake levers.

In general, all the other components (brakes, derailleurs, cranks, etc.) work on the same principles as each other. The differences are in weight, manufacturing and assembly tolerances, material quality/strength, and ...honestly...marketing. All those factors combine to a $300-$500 jump in price per build.

Mo'Phat's pretty much answered it. The "manufacturing and assembly tolerances, material quality/strength" differences do lead to a difference in feel, ride, shift quality/response to those with a lot of seat time. Marketing plays the largest role in differentiation though.

Drivetrain efficiencies...I would expect them all to be fairly close to each other. I vaugely remember seeing a test done at Purdue whose results were in Velo-News (maybe??) that tested a Dura-Ace drivetrain at around 99.7 something% efficient. I would not expect the other groups to differentiate from that by more than 0.1-0.2% Warning! Total "Sales" moment (=pulling numbers out of my A$$)

If someone with too much time verify that possibly?

My take: A lot of it is just marketing bogus. The top-end groupsets look prettier and more "blingy", and they might weigh a few hundred grams less. Then people who ride those groupsets imagine the rest, and rave about the supposed smoothness and crisp shifting. In reality, the performance between the groupsets is very close, minus a few technical details.

From a completely practical standpoint, ignoring the speed designations (8, 9, 10), miniscule weight differences, and judging by performance, reliability, and durability alone, I'd say

A properly tuned..
Sora drivetrain = 90% of Dura-Ace
Tiagra drivetrain = 95% of Dura-Ace
105 drivetrain = 97% of Dura-Ace
Ultegra drivetrain = 99% of Dura-Ace

The rest is just for nit-picky people to notice, none of it makes much real-world difference in the actual cycling that these consumers do.

There you go. Maybe others will have different opinions.

great, thanks for your replies