I don't keep either species, but know people who have both.
In general neither species is to be trusted. They can and will bite.
First of all, wild caught animals are troublesome, particulary Emeralds. Often they will not eat in captivity and die. Stick with captive born.
GTP are easier to keep as their general requirements are easier to meet. They are also more readily available as captive born babies.
Have you considered one of the Amazon Tree Boas instead? They are much easier to keep and would be a good introduction into the trials and tribulations of Tree Boa husbandry. They are cheaper as well and available in a lot of colors and morphs.
Post this query on the Tree Boa forum and I am sure you will get better advice.