If you think you might be interested in sailing with other skippers, and by that I mean racing, a good approach is to go to the AMYA website (
http://www.ModelYacht.org), search out the "Clubs" page, and locate the club that is nearest to you. By finding out what they are sailing, you'll automatically pick a boat that will make you instantly ready to join their fun, provide you with a bunch of new friends, and establish a source of local information and help that will ease your building effort.
If on the other hand, you just want to sail about for relaxation by yourself, the important questions become: 1)How big a car do you have?, and 2) Where do you plan to sail? Either of the two you mention will work well in typical cars of today, and in local ponds that are fresh water if you can find it.
Rod Carr
AMYA #002