I always carry on only. It's simply easier and has enough space for my trips (max 3 week trips). No worry about losing luggage or anything. I also bring a pack-able day pack as well which if absolutely necessary I can start filling up and bring it on as a personal item. The ONLY benefit of checked bags I wouldn't mind having is ability to transport stuff like alcohol.
Also I really don't care about wearing a shirt twice without a wash, especially since a lot of my stuff is wool that I pack. I see no issues with it unless you really stunk it up the first time around.