Derailleurs
 

Front and rear mechanical derailleurs, so many to choose. What makes one model in the hierarchy better than the other?
Weight, spring tension, jockey wheels.... What else?

Weight and quality.

Bling factor and name.

Range.

Perception that it's made somewhere that it's not.

Light, Strong, Cheap

Pick two!

From bottom 1/3 to mid 1/3 - Amount of slop in the hinges, and stiffness in the assembly as a whole. Mid 1/3 to top 1/3 - weight, attention to detail in production. Top 1/3 - bling value, weight reduction, minor (mostly theoretical) construction improvements.

Ok i was going to start a new thread, but i think this relates. Can you use a braze on style FD to a clamp with an adapter of some sort? I am specifically talking about a Dura Ace 7402 FD ?

To give you the most generic/vague answer : quality.

Clutch, capacity

Yes, you just need to know your seat tube diameter. Most bike shop keep them in stock.

Sorry what do you mean they keep them in stock? Adapters for my bike?

I don't know what bike shops stock, but I ordered a generic clamp to attach a 10-speed 105 derailleur to a 1984 Raleigh. Couldn't have been much more simple.

I wouldn't use one on a CF bike, but for anything metal ....

Thanks everyone for your comments. I spent some time reviewing the Shimano road lineup and decided the 105 derailleur is a good balance for performance and quality.
I didn't spend much time looking into Campagnolo and Sram as they are not easy to source in my area.

Your choice of derailleur will be determined by the brand of shifters you’re going to use, i.e. Shimano with Shimano, Campagnolo with Campagnolo, etc.

If you want an adapter to use a braze on type derailleur on a frame that doesn't have a braze on tab you just need to know the diameter of the seat tube, doesn't matter what brand of bike it is.
https://www.greggscycles.com/product...%2414.99%20USD