I say there is a problem within your team (like that "key person" not knowing what is or isn't productive in what he does) that you are hoping to solve through seclusion. Excluding such bad quirks, assuming everyone is acting reasonably (in a tolerant frame of reference), I would say team sized spaces strike a good balance between the peer interaction accessibility and the bad effects of crowd noise.
The problem with our team is that it's not really a team in the traditional sense. We're an engineering office for a multinational and we're a team only in the sense that we have a common manager but all of us pretty much work on different projects, with most of the collaborators being overseas (with a 10 hour timezone difference).
The "key person" is really a key figure and his opinion is valued for a lot of different things, so he's talking a lot to different people. But almost none of it concerns me.
Even if I worked together with the guys I sit next to, I'd prefer that there was a door between me and them. I prefer to work in silence and uninterrupted and if my opinion is required I'd rather work it out before/after lunch or schedule a time slot for it.
