Out of these two the Diamond would be a more reliable choice for getting a quieter animal (there are no guarantees with any snake though) as you are starting out and you don't want to scare your partner early on. I have a Diamond and it has never looked like biting ...(well to be truthful it has difficulty wanting to bite its food sometimes also.....but thats another story...
).
I have a Cape York Jungle which has a good temperament but is a lot more alert and flighty than the Diamond.....We were lucky that she has a reasonable temperament although many do quieten down with maturity and good handling.
I also have a Spotted which is our most bullet-proof snake. She was purchased from a breeder on this site and has the most comatose personality I have encountered. A perfect beginners snake or a snake for people who want to 'ease' the good wife into snake keeping.
We recently bought an adult Murray Darling which has also proven to be a very tame and quiet snake with a wonderful temperament - particularly around our children. She has never looked like biting or becoming aggressive despite never having been exposed to children or a busy household that comes with having a family.
So I hope there is a bit of info for you there - not only on the two you were looking for but a couple of others that I believe are also worth considering.