I'm gonna say get a king >.> Partly cause I love em, a cali king was my first snake... and also partly cause I have some babies for sale lol
Ball pythons are the most boring snakes in existence in my opinion... i know a lot of people like them but they are just SO common... and very.... uninteresting.... a happy bp is one that sleeps all day and rarely moves even when awake. Generally if it is out and about there is something wrong with the enclosure that is making it unhappy so it is seeking a better place to rest. That's just how they are, they sit and wait for food to come by...after they eat they sit and wait to digest...then sit and wait for more food, that is the like of a BP.
In my opinion... people worry WAY to much about humidity with bps... they do not need a high humidity over the entire cage... just provide a humid hide and they should be fine. High humidity over the entire cage causes other problems, as someone mentioned above theirs got scale rot, I've seen respiratory infections which lead to mouth rot in some bp's that where kept in constantly high humid conditions (80% and up). but on the reverse side, shedding problems and again, respiratory infections in bps that are kept in to low relative humidity (less than 20%). What appears to work best is to keep the rh around 40% with a humid hide that provides a micro climate around 70-80%
Sounds intense but it's really easy to do that...
But why bother with all that when you could get a cali king!? Very rarely need to worry about humidity with them, they are damn near bullet proof, very versatile, fantastic eaters, active during the day (although like most snakes, are not going to be moving around a whole lot if they are comfortable in their environment... but a lot more than a ball will) easy to handle -I never understand why people think kings can be aggressive... I've never had one that was a problem, some of my babies where angry little things right out of the egg but already have calmed down and are easily handled. they get aggressive at feeding time.... well duh... most snakes do... and can be a little flighty when this giant hand comes at em in their homes but otherwise.... easy to work with and very calm as adults. My kings have been the best snakes I have ever had for educational talks with kids.... also... can live in a 20 long for their entire life

but ultimately, it's up to you, find something that YOU really like and that you will enjoy.