After flying the M20J getting back into the 172 will feel liek a toy plane and much easier to handle.
Be careful with power-on stalls as the nose breaks pretty hard.
Things will feel cramped inside especially if someones next to you.
The M20J is more stable and much easier to fly in comparison. It has a heavier feel.
The wings are laminar flow which makes them more aerodynamically clean and very efficient at cruise speeds. Descent and speed reductions will take some planning in comparison to the 172.
Flaps are kind of funny too. They are used for every T/O and have no degree detents. Its basically infinately adjustable to either end of the stops.
The plane lands a litle flat too. You'll fly it right on to the ground.
Do you have yuor compllex endorsement yet? you'll need that in order to act as PIC.