I watch both Akame ga Kill and Tokyo Ghoul and enjoy both of them. Don't worry, Seven Deadly Sins is more Shonen-like than Akame ga Kill. Akame ga Kill is more about assassination and corruption mixed with drastic mood swings, ecchi, and deaths. Seven Deadly Sins is about a princess gathering 7 knights (who all have sins and quirks of their own) to fight these Holy Knights. I only read 2 volumes. It's like Fairy Tail somewhat since it deals with adventures and ecchi scenes without the Nakama part. I stopped myself when I decided to wait for the anime.
I think Taichokage has a better comparison of SDS.