A few thoughts. Yes, there have been times that I stood, waiting for a bus to come, when I was thinking 'this is it, from now on I'm renting a car!!'. But that doesn't happen often. I've been to WDW at least twice a year since '99. So, a lot of bus experience. I have also had a rental car with me on occasion.
Yes, a bus can take up to an hour. BUT...not all the time. It depends on many variables. Time of day, when the park opened, how many guests are waiting, etc. If you get to the bus stop just as the bus you wanted pulls away, and it's not at park opening time (say an hour or so after the park opens), then you may have a longish wait for the next bus...could be up to 25 mins!! But the vast majority of the time you may wait for 10 mins and get on a bus, and then be on the bus for up to 20 mins. It seldom takes more than 45 mins, total, to get to a park. Usually it's around 30 mins tops.
The other thing is that this is your first trip. While driving around WDW is fairly easy (things are decently marked), it can be frustrating to new to the area drivers. I have seen many accidents and near accidents when people make sudden decisions on the road due to unfamiliarity. So, you're really better off on the buses until you get a good idea of the area.
I would forgo the rental, and just use the buses. AoA has good bus service. Yes, the bus can be crowded at park openings and closings, but they tend to come a bit more frequently when there is a greater need. Even if you decide to go back to the resort midday, it isn't going to be a huge deal taking the buses. It's vacation.....relax and stop to smell the roses. Sometimes we lose sight of this and tend to rush around, trying to cram as much as we can into one day. Then you miss a lot of little things. So slow down, relax, enjoy each other's company, stop worrying about 'wasting' an mere 30 mins when using a bus vs a car.