Clanad, I think it's fair to say that articulacy, and the ability to think on your feet, are highly regarded as a political asset in this country - which is why the top jobs so often go to expensively educated public shool boys who've spent time in debating societies (and in Cameron's case, working in PR). I'm not personally sure that glibness is praiseworthy; but the electorate seems to think otherwise. The occasional verbal gaffe is forgiven but anyone who made as many as George W Bush, for instance, would be laughed out of office here.
By contrast, would I be right in thinking that a US politician should be "a guy you'd have a beer with"? Which is possibly why people like Gore and Romney don't make it to the presidency: American voters seem more wary of rich kids, while British voters love them and don't envisage having a beer with a politician anyway.
This is meant as an observation, not a criticism. I don't think American politicians are worse than British ones, but I do think they're elected because of different personal qualities.