From everything I have read about Yellow Anacondas, they are much more aquatic and require larger swimming areas for proper care. Also tend to be more defensive that retics and much pickier eaters in general. I don't have one to compare though.
I have a couple of retics and females seam to be the way to go for me. They seam much more mellow (feeding being the exception). I might be lucky though. I have heard stories even on here about some with big attitudes and seen lots of videos of people with grumpy retics. I do provide them a large swimming area though and they use it often. None of my retics are picky eaters. With retics it is a relationship that has to be tended to almost daily to maintain.
My suggestion is to find someone with a few of each and spend time with them to see how they are in person.
I would say both are for experienced keepers (I know, I know, hehehehehehehehe). I have learned a lot with mine.
Truth is it depends on the animal also. Each one is unique and has their own traits when it comes to care and interaction.