Hi Steve,
I would like to first thank you for asking before getting your first snake - or any other creature for that matter.
For you question - there are so many different phythons and boas out there - it would depend on what you are looking for, and most importantly - how much room you have for housing.
I have had both boas and phythons in the past - but had much more room than I do now. So (alas) I am restricted to the smaller snakes (corns, kings, and milks). Personally, I think the ones I have now are more fun. They are more active, and not as "scary" to people who see them for the first time. I love to educate people about snakes (not the ins and outs of each species - just in general)..
This probably didn't help, but thought I would put my two cents in 
If someone told me they wanted to get a snake (first time owner) I would suggest a corn snake - start small.