Do it now, otherwise you're leaving water and corrosives in the sump all winter which will cause no good. Draining from the sump is far preferable to pulling it out through the dipstick hole. Many retro-fit their engines so that the sump drain is piped for easy access.
I would add that the most civilized way to do this job is to motor out on a quiet day for a hour, stop at a well-frequented marina to top up your diesel, come back to dock or mooring and to have a nice whisky.
When you're finished, the oil will still be warm enough to run freely, but not so hot that it will melt your plastic waste oil bottle!
Change the filter at the same time and refill with clean oil. Winterize as per usual.