Adding a dedicated RV power plug. What would you do?

The 50 amp circuit (240v 50a) will probably at least triple the cost of materials. With the 50 amp circuit, you'll need two 50 amp hot wires and one neutral plus a ground wire. For the 30 amp circuit (120v 30a) you'll only need one hot wire and one neutral and one ground. The 50 amp RV circuit is capable of providing almost 4 times as much power. They'll be more more wires and heavier wires needed to be legal.