You asked: "What differences do extended cabs make? And 4 wheel as opposed to rear wheel drive?"
When selecting a pickup truck, you have lots of choices to make.
1. 1/2 ton, 3/4 ton, 1 ton.
2. long bed, shorter bed, short bed.
3. uncovered, tonneau cover, camper top.
3. conventional cab, extended cab, crew cab.
4. 2 wheel drive, 4 wheel drive.
5. gasoline engine, diesel engine.
6. bench seat, bucket seats.
7. and more.
From my experience:
1. No one with a 1 ton wanted to downsize to 1/2 ton.
2. No one with a long bed wanted to downsize to a short bed.
3. No one with a camper top wanted do do without it.
3. No one accustomed to being able to recline the passenger seat wanted a conventional cab.
4. No one was willing to give up their 4 wheel drive.
5. Gasoline engines have improved almost enough, but diesel is still stronger.
6. Bench seats with the movable center arm rest are almost as comfortable as bucket seats, and will allow for 3 across seating.
7. No agreement on brand or color