Stewart_Reptiles hit pretty much everything on the head.
I'll just add my personal experience...
I have 2 Boaphile enclosures that I really like. They're super light, super easy to clean and look nice.
They do use a thinner PVC than AP and some others, but they're well built in my opinion.
They hold heat and humidity really well, but my understanding is APs thicker PVC retains it even better.
I've been a glass guy for many years, but since acquiring a few PVC enclosures I'll never buy glass again.
And I definitely think a RHP is the way to go. They run more efficiently and create a nice temp gradient using just one heat source.
As for height, many people go with the 12" height for BPs since they're primarily a terrestrial species. But I have heard many people say the 18" height is much easier to clean in the back corners, etc...
As for doors, I'd say acrylic as well.
Sliding or drop down is really personal preference. With my BPs either is fine, I honestly don't have a preference.
With my Borneo STP I definitely prefer the sliding door due to his strong feeding response.
I plan to use sliding when my Bredli and Carpet are large enough for their "forever enclosures" for the same reason. It's just a little easier to contain a hungry snake with a strong feeding response with sliding.
I think I answered all your questions, but if I missed anything please don't be afraid to ask.
From what I know of AP, they're the cream of the crop though. I'll be adding a few over the next few years. But I wouldn't hesitate to buy another Boaphile either.