Hard to pick since each one serves a different purpose and need.
Suicide Squad are super villains chosen by the government for dangerous missions in exchange for reduced sentences and if they step out of line they get their head blown off.
Secret Six is a logical spin off of Suicide Squad; a group of villains who broke off from the Squad and do hired gigs on their own terms while only having each other to rely on.
One of them like being under contract and the other is like being a freelancer.