i say if you are only interested in a single snake I get th visible morph( so that dropes the 100% het pied) since you won't get a pied until can either breed it to another 100% het pied or pied.
I also would be looking at a couple things if going with a rtb, The likely hood of the family getting tired of it ( this size snake does scare people from visiting even if they know it locked in another room) My mother got friends that refuse to visit her cause of the boa I rescued. I also would point out once it gets so large it will need something along the size of a 8x8 room for a comfortable cage. I found that mine prefers to roam the room and such versus staying in her 2x4 cage. I don't take her outside as much now cause it does freak the neighbors out when they see her from a far( one neighbor is really scared but his daughter wants the snake lol..)
I think the main issue to consider is future funds for food, current and possible area restictions that may be. I know my rtb she only 7-8 ft long but she would eat 2 large rats or a full grown rabbit if I had them to give her all the time. (locally I know large rats are at least 8 bucks each and I not prices a rabbit as a feeder since I know they not cheap.