It's called inclusion body disorder, and it's a very bad, contagious disease that associated with boas. It can hide latent in your boa for over a year, and is fatal. It can spread to any other boas or pythons you have in your collection.

But to add my two cents to your original question, boas are typically amazing eaters and very calm. If you don't mind the obviously larger size and hense the larger enclosure and food that comes with it, I think they're easier to care for than BPs.
My biggest suggestion would be to go handle some adults (remembering that there are big differences in final size between a male and female) to make sure your comfortable with an animal that will reach that size.