It is not possible to point at one app as the clear winner. Each and every application has some good quality and also some features inferior to the others. And the beauty of free software is that you can try to test them and see how good or bad they are. What we would recommend you is to read descriptions of all the drawing apps and also of the online tools, narrow your choices down, and then install them and see what works for you and what does not. We made sure that these apps are not humongous in size, so as to not chug your data.