Thank you Zach for asking some great questions!
Q: What is the benefit of having a compost bin over just a pile? I ask because it seems like it would be easier to turn a pile than compost in a bin.
A: An attractive bin is nicer to look at and is a preemptive strike at better relations with neighbors who might otherwise object if it is visible to them. Some bin designs (very few) help with air circulation and speed composting.
It is easier to turn a pile. Some bins are so poorly designed that they should be tossed or relegated to finishing. My working pile is an open pile, my finishing pile is a basic (slightly undersize) bin that works fine for finishing but would be a real pain for the active turning stage.
Q: What are the benefits/downsides of keeping a compost pile in a relatively sunny area versus a relatively shady area and why?
A: Sunny vs Shady does not really matter. More important is a balance between ease of access (getting compostable waste to the pile), access to areas where finished compost will be used, and being unobtrusive to visitors and neighbors if that is important to you. The final and possibly most important tip about pile location is that the pile must be in contact with the ground. All of the microbes, insects, arachnids, and worms that drive the pile get there by moving in from the ground up. This is one of the reasons rotating or tumbler bins are useless, the compost ingredients are not in contact with the soil.
Bonus tip for open piles: The pile should be covered to prevent over-watering in rainy areas/seasons and over-drying in dry areas/seasons. A 14×14 foot tarp should work well for a 3x3x3 foot minimum sized pile. An open pile will really be more of a pyramid shape when freshly turned and closer to 5×5 at the base.