I voted blood. I have a BCI and a Borneo short tail so it depends what you like.

The Borneo is a big lazy slug that has the unnerving habit of watching you where ever you go. They are different to handle than a boa in that they don't hold onto you at all, so you have to be very diligent about supporting their entire body (no throwing around your shoulder).

The BCI is very active and outgoing and will climb all over you and anything with in reach. He's also a lot quicker to strike and does so with less warning than the borneo.