King's Indian, Grunfeld or Nimzo Indian? Beginner Play

I'm wondering if someone could explain to me the relative merits of these three defenses. I've been mostly playing the Nimzo Indian but I want to consider all three to take a deeper dive into and use more consistently. It seems to me that the Nimzo has the most early game variations because many players will try to avoid it, so focusing on the KID or the Grunfeld may be easier to learn for a beginner.

I'm not sure if this helps in any way, but I use the Sicilian Najdorf when playing as black against E4. Thanks!

I asked a similar question of some of the 2000's at my local club and they gave they all gave the same answer.  They all said study the Grunfeld over the KID because the KID is closed and makes development more tricky, especially for beginners.  I didn't ask about the nimzo so I'm not sure about it.  I took their advice and started working on the Grunfeld.  

They also said to make sure I don't slack up on studying tactics and middle and endgame strategy.  It's much more important to get an understanding of tactics than openings.  

I employ the French against 1. e4.  

"... Is the King's Indian the opening for [you]? ... If your attitude to playing Black in chess is to try to neutralize White’s slight advantage by careful defensive play, then the answer is no. In that case you should be looking for a book on something like the Queen's Gambit Declined or the Queen's Indian. If, on the other hand, you are a bit of a risk taker, you want to battle for the initiative right from the start, launch counterattacks rather than meekly reacting to the opponents threats and lure White into over-extending himself, then the answer is a resounding yes! ..." - GM Joe Gallagher (2002)

https://web.archive.org/web/20140627055734/http://www.chesscafe.com/text/hansen38.pdf

"... The [Grünfeld] theory is very well developed of course due to the attention of so many strong players and therefore perhaps likely to scare away many new adherents. ... There are some details missing [in a 2002 Grünfeld book], some more important than others, but in general there is enough for people to take on the opening as Black. ... In order to get enough use of this book, I would say that you should be rated at least 1600 ..." - FN Carsten Hansen (2002)

https://web.archive.org/web/20140626181639/http://www.chesscafe.com/text/hansen40.pdf

King's Indian

I play Nimzo, and sometimes Ne4 Budapest, but if they dont do 2.c4 I transpose into king’s Indian. 

I play Alekhine against 1.e4, and Alapin as white against Sicilian.