I vastly prefer t-shirts and BDUs/dark dress slacks/whatever you want to call them. I've also used polos.
Honestly, I don't think wearing a nice button down with all the bells and whistles on it is all that its cracked up to be. Nurses and doctors wear glorified pajamas because healthcare is very messy work, and in EMS you're also outside a lot, which can lead to sweating, getting dirt on your uniform, etc. A tshirt/uniform pants combo shows professional uniformity between crews and practically, you can change out a duty tshirt easily. Looking the same, I would argue, is better than looking fancy.
People talk about lacking professionalism in EMS, but a nice shirt is not going to fix that. I would be beyond shocked if the public even processed the difference between a crew with white button downs, polos, or blue tshirts. It's more important that the crew looks uniform, and acts professionally.
That being said, if you're a volunteer (or god forbid a paid guy) who shows up in a wife beater and bunker pants, I hate you.