I think the "collecting" part is highly subjective. I also believe, it really doesn't matter if you have an interest in highly collectable stuff or stuff that isn't, you should collect what interests you. If you are collecting to make a living, that is an entirely different matter.

That's why in this thread I was sticking to function. 2 sets of Universal calipers from the same era, one will stop you well, the other won't. Derailleurs from the same era, one shifts better than the other. By knowing why one component works better than the other is good knowledge to have when making a decision, and I find it interesting.