Help Purchasing A Dash Camera With DVR For My Delivery Automobile

I will be starting a new job and I believe that having some sort of dash cam is going to be the best way to add a degree of confidence and also peace of mind as I am out on the road. I am going to be delivering merchandise to clients, while at times transporting clients to and from appointments.

Will a dash camera with DVR deliver all the recording power I needed in case there may be some form of accident? I want to see about having recording ability that captures both the view from the front and rear. Any ideas shall be valuable.