Theory's article on the blog made me think of this.
Think about Measurement and Metric System. Their names and functions are very similar. However, in terms of splaying, Measurement is actually the better card. It has lower requirement (one card in hand vs. more than one card in green on the table) is more flexible, (don't need to splay green first) and has more potential (can draw a high age card.) But why is the better card sitting at a lower age?
Truth to be told, between the two cards I actually like the metric system better. And this has everything to do with its symbols. Crowns and Factories are just that much more important in the middle ages. And I think it is more than justified to put the metric system at the higher age just because of its symbols.
There are a few other examples I can think of which also show a similar intricacy.
For example, there are only two factories on Industrialization versus three leaves on reformation. Both cards can tuck and splay. The fact that Industrialization is draw and tuck makes it 2 ages higher and one fewer icon.
Also, think about Alchemy. It is a strong card, but the fact that it cannot draw red cards actually somewhat balances it. If it says green instead for example, then it will be a bit overpowered.
Do you find any other examples where small design choices make big differences in the game?