Hello and welcome! Sad to see your car in that state, but since you are safe som the accident and it trigged you to buy a new car I guess it's ok
I have a Cooper S myself and a F20 120d, so I know what you are talking about. I would say if you are looking for a true replacement for the Cooper S, pick the 125i. There is of course more torque in the 125d, but the fun factor is higher in the i when it comes to active driving.
I use my 120d as a daily commuter in urban traffic, so the diesel is perfect for me. But if you'll have a Dacia as your work horse, I would buy the 125i as a touring (and family) car.