"Neat-casual" was my vote, and there's a few reasons for that.
1. Professionals are required to look professional.
I'm going to be starting my career in engineering (preferrably structural) very shortly, and over the years of my undergraduate degree I've been made aware of the dress conventions for the profession from a variety of sources. The key point is that professions are held to a higher standard than the average person, so you have to dress & groom yourself enough to show that you care for yourself. Wearing sweats might be comfortable, but it doesn't nothing for appearances. Anyhow, I'd extend the same principles to medical doctors.
2. Being a medical doctor, looking clean on the job is essential.
This one somewhat goes without saying, but it's true. As uncomfortable the prospect of a proctology examination is (not looking forward to that in any case, and to give a hint... white glove, *snap*), it'd be even worse if the doctor doesn't look like he's cleaned himself prior to giving you "the probing".
3. I don't like wearing the full monkey suit myself.
I hate having to wear a tie; or more accurately, I hate having to do the top button up on a collared shit (which is required if you're wearing a tie). That and I find the standard business attire just doesn't feel comfy; it feels thin & flimsy (a bit airy too), and I'm more partial to attire which feels more "robust" (if that's the right term). Maybe it's because I've worked a more jobs in the field (both grunt work & technical) than in the office, and wearing clothing the finer clothes makes me feel under-dressed or unprepared; I guess doing the "dirty work" over the years just makes one accustomed to it. Anyhow, like the first point I'd extend the same principles to doctors as I would myself... well, maybe a little bit better dressed because they don't do field work (but not much).
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When it comes down to it, looking clean with a collared shirt is about it; no need for long sleeves or the white lab coat, looking professional doesn't mean wearing the full business attire all the time. After all, it's called "business attire" and not "professional attire"; let the bean counters wear it all they want, the real professionals know they don't need it all the time.
The only real question is whether or not medical doctors should be permitted to wear blue jeans (or if they should wear slacks/dress-pants). Those are usually considered more "working" clothes, and do make more sense if one does field-work; those might be a bit too casual for doctors, slacks/dress-pants are probably a better idea. Not much is really needed beyond that, it's just unnecessary.