I would recommend a car. There are some bus companies that offer service between Surfer's Paradise and BNE - but I think it needs to be arranged. It is a couple of hour drive. A taxi would be way too expensive.
The Marriott Resort is not on the beach. It is on the north end of Surfer's Paradise and too far to walk to the main shopping, restaurant area. So you will likely need a car to get around. While this property is called a resort, it is really a regular hotel with a tiered parking garage.
The Courtyard has a great location in the center of everything - next to all to new shopping areas and condos. The Courtyard is however not a top notch Courtyard. It is a 30 story hotel with balconies. Rooms are OK - but not that great - hotel is slightly run down. If you have Plat/Gold status you will get an ocean view. I stayed at the Courtyard 3 months ago - and ruled out the Marriott for being too far away.
The Marriott Surfer's Paradise Resort since it is a resort Plat/Gold do not get access to the Lounge. See the Ts&Cs.