Nanatsu no Taizai includes others races like: faries, giants, demons etc.
Although I have yet to read the manga, perhaps it includes more ecchi like Fairy Tail. For those who are bothered by the plot distracting ecchi, while watching nanatsu no taizai, I found the ecchi more bearable and less frequent. Both Fairy Tail and Nanatsu no Taizai are ecchi(the mangas are labeled ecchi). They both involve magic and it's easy to correlate Fairy Tail's and Nanatsu no Taizai's magic to each other.
The transition to Fairy Tail to Nanatsu no Taizai is easy. I would definitely recommend Nanatsu no Taizai(Seven Deadly Sins) to any Fairy Tail fan or to anyone who was disappointed by Fairy Tail. I'm not a big fan of Fairy Tail, but I acknowledge that this anime has a fan base. In the past, after hearing about Fairy Tail, checking out the wiki and watching a few chapter reviews for a while I eventually decided to check it out.
