I feel like Secret Six is an evolution of Suicide Squad and as such, ignoring the quality of the writing and art, is stronger concept than Suicide Squad. Obviously it doesn't mean that its always going to be better, for example now Suicide Squad is better book overall since it has strong creative team while Gail (in my opinion) reached her creativity peak in pre-Flashpoint Secret Six and now is just trying to relive her best days, she also doesn't have a reliable partner on art.