I have them both and whether it's worth it or not depends on what you are trying to do with them.

If you want to give your boa an opportunity to climb in the enclosure then it's worth it. It's also easier to work in the enclosure with the extra height.

However, the extra height means much more space to heat and humidify - I work 3x as hard at keeping the tall cage at the target levels than the short one. In fact, I found that the tall cage would not heat up enough with just belly heat due to the large space.

As for adequate size for a 7 footer, I can't answer that but hopefully someone here will know