Your stock tire size is 225/50/16.
The 215/50/16 is 1.57% shorter. The speedometer would read 1.589% too fast.
This is an acceptable trade.
The 215/40/16 is 8.38% shorter. The speedometer would read 9.127% too fast.
This is a dangerous tire on your car.
When changing tire sizes, we recommend staying within 3% of the diameter/height of the original tire. Any more than this and you face the risk of brake failure.