New answers tagged drop-down-list
I find this to be helpful. http://msdn.microsoft.com/en-us/library/bb158706.aspx What's important is to remain consistent.
If the question is taken at face value, i.e. strictly a choice between the →/↓ arrows or the +/- signs, then I suggest using arrows. Arrows denote the direction and a sense of movement to another place or view. +/- signs could be construed as meaning add / remove. For example it looks like I can add a manufacturer, or add an Extra item. While, the minus ...
I don't have any "official" or user tested information about this, but in the examples you have detailed in your question, the sentence case works well for answer which are based around a response you would generally hear someone speak. It makes sense that "value" answers would be capitalized. i.e. Express Delivery Economy Delivery
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