@ Ebierly & Tev9999
Something to consider when choosing the type of recessed lighting for your project:
Lighting is much a personal preferrence - there really is no right or wrong, its about achieving the look you want, as well as the lighting offering you what you need.
Everyone here most likely has their own opinions on the recessed can sizes.
What we can agree on is that by deciding the look you want (style of the trim) and the effects of the lighting in a given room or task, that may narrow down your options for you.
Installation plays a big roll. What is in the ceiling space (insulation, hvac ductwork, plumbing pipes, electrical wiring)?
Layout of the recessed light cans?
Most manufactures will give you the specifications regarding the room coverage, as well as recommended spacing for the fixture. Does it mean you can use more or less, sure!
My suggestion, while not answering your question directly, is to visit your local lighting stores and see whats on display. Figure out the style you like, as recessed lighting prices vary dramatically, figure out what fits in your budget.
Hope this helps!