To clarify for others, an open unit is one in which anyone (usually restricted to neurology and neurosurgery/NIR) can admit to the unit, and the NCC team acts as consultants. The surgeon or neurologist remains the primary service, and can choose to ignore the NCC team's recommendations if they wish. In a closed unit, all admissions go through the NCC team, and when patients enter the unit, the NCC attending becomes the attending of record. Attendings admitting to the unit therefore place implicit trust in the NCC team to do the right thing. There are a few more layers to this, such as the responding vs. responsible clinician issues imposed by JCAHO, but this definition should suffice.
In practice, attendings in an open unit usually do listen to the NCC team, and the NCC team in a closed unit often makes concessions for the preferences of the patient's other physicians (i.e. if the surgeon that did the case that landed the patient in the ICU wants a scan, then the NCC team gets the scan). At the end of the day, many ICUs do not fit cleanly into either open or closed, but rather adopt a hybrid model. This is necessary in some cases because neurosurgeons have historically not wanted to relinquish primary control of their patients to a neurologist/neuroanesthesiologist. This view is slowly changing, however, as the surgeons realize that we're actually pretty good at it, and it leaves them free to focus on OR cases.
In my opinion, closed is better because control is power. However, with that control comes the responsibility of dealing with all the little details 24/7, and doing all the procedures (except for EVDs and bolts, usually). In an open system, the admitting services are in control, and so they have to focus on the details. Some would argue that this is better for the NCC team, because it leaves them free to focus on troubleshooting the active issues without having to deal with requests to replete the K+ every 5 minutes. In a lot of open units, the procedures get done by the admitting teams, so if you aren't procedure-oriented, then you might think that's a plus. Most NCC people like procedures, and there are, in fact, some open-ish systems in which the NCC team gets first crack at the procedures.
I think that for students picking a residency, open/closed ICUs should not be too much of a factor in your decision, even if you are interested in NCC. There are plenty of opportunities for ICU exposure either way. For fellows, it is much more important because it factors in to your day-to-day activities and how you interact with other teams and your patients.
I think that most residents/fellows you ask will think that their system is the best. As in all things, you'll have to decide which works best for you.
