First, a cold engine will have more oil in the pan than a warm one, therefore a more complete drain. It takes hours for all of the oil that is going to leave the engine parts to drip into the pan. You can observe this by checking the dipstick after shut down and then again before you fly next. Not sure how hot oil will drain the pan more fully than cold, though it will do so faster due to the lower viscosity. If you are most concerned with maximum oil removal, do it when cold.
Second, it is not a problem to leave small amounts of old oil in the pan. The oil's lubricating effectiveness has a usefull life, WAY longer than our drain intervals. We change it so often, because it quickly becomes saturated with debris, such as lead, carbon, and oxidized oil and once saturated, will increase sludge build up.
Last, the oil keeps debris in suspension and it does this equally effectively at any temperature. If it didn't, all of the debris would fall out during periods of non-use and form sludge. Sludge is typically formed when oil is fully saturated (the disspersents hold debris in suspension, but can only hold so much) and any further debris falls out and settles on parts. The oxidized oil component of the debris is very gooey and helps form a syrup/paste that clings. An oil change, whether at 0* or 200* will not pull sludge out of the engine. Non-saturated oil can occasionally pick up particles from the sludge and hold them in suspension. However, this happens while the engine is running and has nothing to do with the oil change process. Most sludge, once formed, is VERY difficult to remove without mechanical cleaning or agressive solvents. It's primary evil is that it hampers the oil's ability to remove heat from the parts with sludge, as well as plugging small passages.
I am not suggesting one method or the other. Just pointing out some facts to help others with informed decisions.
Larry