Iron-ons tend to peel off easily if not washing properly.
I love silk-screening because they LAST and it shows good quality of the print on apparels.
In my high school, i used to make design and silk-screened them because there is a lab where you can use their inks, machine, et cetera (unforunately, that class had been cut due to the budget... *fuming*)
understand this: the process of silk-screening is DIFFERENT than just iron it on. You make an image that is black and white only... then you "imprint" it onto a screen that has a sheet of silk onto it and then you choose which ink you want for certain portions of picture... some would just like one color for the entire image while some would like to have this to be red, that to be blue (LONGER and CAREFULLY process because you have to cover other parts to prevent from being inked) so the images I am showing don't look like that on actual tee-shirts...
(I actually have more but I dont make them on a computer.. they are done on a special paper *cut out beforehanded to create an image* that can be pasted onto the screen to serve as a modular for making many shirts.)