When one watches House and Senate hearings, one soon notices several different methods of questioning:
1. The question that is a statement worded so that the person being questioned will/can answer only one way. These are generally self-motivated statements that are either thinly disguised praise of the policy or issue in question or even less thinly disguised disgust with the witness.
I think everyone I've watched has, at some time or another, read prepared questions. But even here, there are differences. In some cases, Jim Bunning and Richard Shelby come to mind, they seem not to have read the questions beforehand and more than occasionally, don't seem to understand what they are reading.
The most engaged and brightest people in Congress usually ask questions without notes that demonstrate both their understanding of the issue at hand and their attention to the matters under discussion... which is not to say that a lot of dumb questions don't also get asked.
Best questioner: Dingell in the House. Whether he reads prepared questions or asks them off the cuff, they are almost always short, direct, and to the point. Most hearings could be cut in half if other members followed his lead.
Worst questioner: Emmanuel Cleaver, without question. Mr. Cleaver is one of those who rarely reads prepared questions but ought to because he hems and haws and doesn't seem to know when he starts a question, even if he has been present through most of the hearing, where he wants to go with it. Watching and listening to him is painful. He actually makes George W. Bush look good.
Alan Grayson comes in a close second. On the House banking committee he routinely embarrasses himself. Grayson thinks he knows how to read income statements and balance sheets. He doesn't. And the poor witnesses, usually financial experts of one sort or another, are faced with the unenviable task of trying to answer a question so stupid it is meaningless without telling a member of Congress that he is a blithering idiot.