BPs are actually great eaters if you get their husbandry down just right. I've had two of my Ball pythons picky at the start, but they eat like pigs now.

For a 6 foot full grown boa, I'd go with a BCI male. As stated above, they do make great pets and are very placid snakes. My BCI male is great and hasn't ever refused for me. He's a true pig at heart.

Green Tree pythons or Emerald Tree boas aren't bad, but I wouldn't consider them to be a beginner python or boa. They are more at an intermediate level for keeping them.