So, Chuck, you are saying (or meant to say):
if you learn to fly on a Cub, you will be able to fly a 172. But if you learnt to fly on a 172 you won't stand a chance in a Cub.
Well...............
That's a good reason to learn in a 172! It is easier!
It's the same reason you learn to drive in a simple small front-wheel drive car rather than an Audi Quatro, a Landrover or a rear-wheel drive.
(We have another saying over here: if you learn to fly from our - really crap, bumpy, lumpy, short, uneven, wet, boggy, narrow, curved... airfield - then you can fly from any airfield!)
Some people see that as a unique selling point. I see it as: "we operate from a crap site"!
A final word: as an instructor, side-by-side instruction adds an extra help to student/instructor interaction. You can see their face much more clearly, to start with! And I have a couple of thousand hours teaching in a tandem seater.