Tether diameter question

Hello! I am new to ROVs and I am looking for a simple explanation of the advantages of a thinner diameter tether. I understand the less drag the further the ROV is away from shore. I also understand the longer my tether is the more power loss I will have sending power to my ROV. Is there an easy way to illustrate this? If my ROV has a 4.5mm tether that is 300m meters in length and I have another ROV with a 10mm tether and is 300m in length, how do I quantify performance issues, loss of power to the ROV? Any suggestion would be super helpful. Thank you in advance for your help!