No worries, I enjoy answering questions about them!
I like to think of it as being Green Tree Pythons looking like Emerald Tree Boas. :D
Seriously though, they are both arboreal boids, but they have several differences, as well as similarities.
Starting at birth, and before hand. Green Tree Pythons are oviparous (egg layers), while Emerald Tree Boas are ovoviviparous (live birth). Emerald Tree Boas are also larger and less fragile at birth.
You should not handle Green Tree Pythons because possible damage to the spine. Vs. Emerald Tree Boas who can be gently handled. As long as you have a removable perch, and don't try to unwrap them, you can technically "handle" both. :D
There are cosmetic differences as well. Green Tree Pythons have a short, stocky head, large bumps above their nostrils and a more pronounced spine, along with other things (such as color).
http://ball-pythons.net/forums/showthread.php?t=83851 Green Tree Python
Temperament is debatable. Some say Emeralds are calmer, others say Green Tree Pythons are. I believe both species, depending on the individual animal, can be calmed enough to manage them.
Price, they are quite similar in. Locality of the animal plays a large part in price. A Northern Emerald will run you around $400, and most localities of Green Tree Python will run you similar ($300-$400).
As far as care, I'd say Green Tree Pythons can be a little more difficult, especially as neonates. Once they are adults, both become quite a bit easier to keep. :)
http://www.sprucenubblefarm.com/chon...ncaresheet.php Green Tree Python Care Sheet
http://www.emeraldtreeboa.org/daemons/etbcare.htm Emerald Tree Boa Care Sheet
