I've led courses on spatial data analysis and mapping using Excel+QGIS, as well as using R, sometimes covering both in one course. Its definitely hard to convince students the value of R when they are used to being able to see and interact more directly with data.
I usually explain that using Excel + QGIS is like baking a cake yourself. You do all the steps yourself, and if you realize at the end you forgot to add eggs, you have to throw the cake out and start all over again.
Using R, on the other hand, is like writing a recipe. If you forgot a key ingredient, fixing the recipe is as simple as adding it to the list of ingredients. The catch is that you hand the recipe to a very stupid and literal chef, so you must specify everything in the recipe perfectly.