My question is : are there applications where Arduino is best suited?
Seeing how no one in North America has ANY in stock ... if you have a project you want to do now and/or want to assure you can find the actual board for the next one you want to build, best to go with tried and true arduino.
Also .. really any project that you don't need the speed, etc for .. you will be better off at this time (IMHO) sticking with arduino until you run into limits you can't get around with sheer programming genius.
That said . .I am watching close and will order one when they come available due to having an actual need for such horsepower for some projects.