Dress shirt fabrics
Do you get more utility from an Oxford shirt or a poplin? Chambray or denim?
An Oxford shirt does about the same things that a chambray dress shirt would offer. They feature equivalent levels of insulation. They have the same closure: a button placket. Until you start weighing the cultural references they make, the choice seems without distinction.
Picking a shirt is a lot like putting your thoughts into words. Words give similar ideas entirely different lives, meanings, resonance. You can convey similar ideas with words so differently that they're received in completely different ways.
These small differences matter in fashion because we're dressing more for cultural context than functionality. It's hard to keep these details in mind, which is why I find it useful to explain these terms in contrast to each other.
Onto the cloth!
Oxford isn't a generic term
"Oxford" might be the Kleenex of dress shirts: a marquee whose name is used to define a much broader category. Just as paper tissue is commonly called Kleenex even if it's not, dress shirts are identified as Oxford whether or not they're made of Oxford cloth, the main marker of an actual Oxford shirt.
Oxford has a rugged feel with a body that lends structure to a shirt. It gives you the best of both worlds: no worries as far as keeping the shirt meticulously ironed and structure in the button placket + collar to give your look more definition.
Since it's a casual fabric, I feel more comfortable with Oxford shirts for day. This convention invites deliberate exceptions for cocktails, like pairing an Oxford shirt with sequined pants. The Oxford shirt may be too casual for cocktails and the sequined pant too formal, but together, they strike a very compelling balance.
Poplin vs. Broadcloth
While both have a simple weave, poplin is more refined. Made from higher quality, finer cotton fibers, it's the more often used in luxurious pieces. Broadcloth, on the other hand, is your everyday workhorse, from a grade horse to purebred. The differences between poplin and broadcloth are very subtle, and I'd be surprised if I have anything but broadcloth in my wardrobe. Excellent broadcloths are out there!
If a shirt label simply states "100% cotton" without further elaboration, chances are you're dealing with broadcloth. "Broadcloth" is a trade term. It refers to the width of the loom used to weave the fabric. It doesn't indicate quality for the ultimate consumer.