If tameness is what you are after, you can't go wrong with Arg B/W, Arg Red, or Blue, or Hybrid (Red x Blue). Any of these will be easier to tame than a Columbian.
The tricky part is that there are individual differences in each animal. It is really a personal preference which species/color to get.
In my experience an with talking to others, it seems that Arg B/w are mostly very tame from start to finish. I think that Reds are sometimes not as tame as B/W when they are hatchlings, but apparantly tame down quite well (I didn't keep mine long enough to find out). I have no experience with Blues, yet, but possibly people are refering to great feeding response as aggression. Some have told me that they are more hyper, but I also heard that they calm down nicely when they get bigger. I recently got some hybrids a week ago, so I don't know yet, but they seem handleable, but at 2 weeks old, they are flighty.
I am a little biased, as the very first Arg B/W I had was tame from day one (I got her when she was 2 weeks old). That one would always casually walk around my hand, even the instant I picked it up. I later sold it to people whose kids slept with it on their bed.
Oh yeah, I had one Columbian that was very tame, but that is definitly a rarity.
As for care differences, Stella wrote an excellent post comparing the levels of care necessary. You can do a search for "Ron St.Pierre".
Dave