According to me, there is going to be a tough competition between BJP and AAP. Clearly, the Modi wave has been dominating over the broomstick in the past few years but considering the development done by AAP in Delhi, the voters are happy. Government schools in Delhi are the best example, which have been raised to a standard better than the private ones. The recent scheme of free Metro services for ladies is also a hit among voters.
Although Lok Sabha results showed a clear BJP dominance in the region, there is a big difference between Lok Sabha and State elections. Congress has no chances to win. There is going to be a tough competition between BJP and AAP. There are still eight months left for the elections, so it all depends on how the Delhi government can woo the voters and gain their trust. Also, the BJP government at Centre has a really good chance to woo the voters and the name 'Modi' is enough to cause jitters in the AAP party. The recent internal spat in the AAP party can affect the party's show at Delhi whereas Amit Shah is the man who keeps BJP together.
Since I live in the northern part of India, I think AAP is going to win again.