A bit OT to lounges, but I'm a PT user myself from OOL and absent the skybus operation which was a door to door service (but much pricier of course) that got killed off what 3-4 years ago now? getting into GC proper/Broadbeach/Surfers etc is actually really simple and very affordable. The 777 bus leaves OOL every 15 minutes pretty much the whole day and connects directly to the tram at Broadbeach and from there you can get up through surfers up to the theme park area. There's also the 760(?) bus from OOL, but I think that goes more the other way (I connect to the tram and it's simples). Cost of under $5 to get to surfers and if not with a lot of luggage is perfectly acceptable way to do it (though the 777 bus also has *some* space for luggage, and can roll cases and so on onto the tram. It's so convenient (I guess set up for the comm games more or less) that it's my go to. Walk off the plane, out the terminal and pretty much onto a bus within minutes. Can be at hotel in around 40-45 minutes depending on where in the area I'm staying.
Now from BNE, yes the train goes right down, through BNE, to the train station there, but that's a little more complicated to navigate, and definitely more costly for the airtrain. It also takes longer to/fro than OOL (but there isn't the road component). Sure BNE has far more options and better (mainline) service and that's definitely a distinction, but I just find OOL so easy to get to with rarely any kind of delay or issue.
Indeed if going into the heart of surfers and staying in that area, it probably would make more sense with this as an option than renting a car and finding/dealing with parking and all the rest (but again, if one wants to go exploring more up/down the coast or hinterland, then a car is going to be a must, but if just going to stay in that general area between Broadbeach nd Helensvale, I'd almost say one doesn't *need* a car - the tram and busses run pretty well to get to most places. They're electric, clean, friendly drivers and I've not had a problem in many trips (except if I screw up the touch off at Broadbeach South before touch on the tram, but you can get that fixed via the go card website and they are really responsive).
Currently it's best to use a Go card for this kind of trip, but already one can use contactless cc's for the trams and I'm pretty sre this will be extended to the busses too at some point, so it will be like Sydney or London where one can just PAYG with via contactless, and it really is very cheap compared to many places.
so I echo the vote for PT to/from OOL.
(also sale prices, specially in J, are generally much cheaper than BNE when they crop up)