I think one should play an opening one i comfortable with so I would say Grunfeld in this case.

About Nimzo I would say that id depends on blacks preferece in most cases since most variations can be played in several styles (Queensgambit style , QID style, Bogo Indian style, Benoni style, Dutch style, independent style). Nimzo is often played as a solid variation but there are lots of sharp black gambit lines as well.

Also black does not have to play QID as partner to the Nimzo. Black has several other options.
* Play Bogo Indian = most economical but possibley not objective best.
* Transpose to Tango with Nc6. However it depends on black prefernce vs Qc2 Nimzo or Nf3 Nimzo. Also black is commited to Catalan accepted.
* Transpose to QGD/Catalan with d5. The Point is to ruling out exchange variation with Ne2 plan.
* Transpose to Blumenfeld gambit. However this line is often considered dubiois
* Transpose to Benoni. It rules out pawn to f4 line. Drawbacks of Benoni is that it would possible requare much work = impractical

If the question is more purely workload, I think that the Grunfeld is less work, though to some extent it depends on which variations of each defense you choose.  Generally, theory in the Grunfeld is narrow and deep, while in the Nimzo/QID/Catalan complex it is extremely broad and covers many more types of positions.  You have to be able to play a much wider type of positions to play the Nimzo/QID/Catalan well than the Grunfeld, in my opinion, and often White is the one who gets to specialize in his approach.   

You will probably end up learning more about chess from the Nimzo/QID, if you actually make a serious effort to study the nuances of all of the types of positions you come across (IQP, Benoni-like, "light squared strategy," dark-squared blockade, Dutch-like, and on and on).  It's a monumental task, but that's why it's so instructive!

But my last post was meant to convey that these are radically different openings, so it shouldn't be too hard to choose between them, in my opinion.  

Lastly, I bet you'll find that you actually get Grunfeld positions more often than Nimzo ones in practice.  For myself, it was very discouraging to spend so long working on the Nimzo-Indian and then always see 3.Nf3 or 2.Nf3.  In my opinion, if you want to play the Nimzo you should love your defense to 3.Nf3 just as much as you love the Nimzo, because you're going to see it more often.  

And I agree with Bryan that the d-pawn specials are much easier after 2...g6 than 2...e6.

@ErictheRed - I understand your point, I think; the question is, strictly speaking, intended to solicit opinions on which defence has the greater study workload.
It's not really about which defence is 'better', as I accept that to be a pointless debate, essentially, when discussing such mainstream openings.
Thanks for the summary points about each characteristic of play, these are all useful reminders, as my preference lately seems to be the Grunfeld but I also know that there are some facets of play there that are more difficult for a player like me than in the NID/QID.
I enjoy openings selection discussion greatly and welcome players' thoughts on these defences in all contexts, but I also realise that at my level openings aren't as important as other parts of the game.
I still like to dwell on them, though!
So my apologies if the question is puzzling, I admit that the selection process in these matters is puzzling to me too, as I have, at various times over the years, felt that I should play either slower or faster paced openings, hyper modern or classical, pawn chains or not, etc., I think I'm still trying to 'know thyself' in this game...
However, posters here have been their usual patient and helpful selves with me, so thanks for that - as stated previously, the original question was aiming at the theoretical workload of the two complexes, so any further comments on that would make interesting reading.
Meantime I'm going Grunfeld, I believe.
Cheers

slates wrote on 03/28/14 at 23:16:23:


One very good point about the Grunfeld is that it can work very well against players who don't know a lot of theory, but just play solidly in Queen Pawn positions. So whilst a plan of playing d4, c4, e3, b3, Nf3, Nc3, Be2, Bb2 can work reasonably well against a Kings Indian, against the Grunfeld that's asking for trouble. You go c5, Nc6, Qa5, Ne4 maybe and you are blowing them away before they've escaped the opening. The problem against people who know what they are doing is that Black can just get smothered and have to defend difficult technical positions.

Here's a personal example from quite a long time ago.

At the time, the player of the White pieces was around 1600-1800 standard and Black around 2000.

If you think your game needs to be improved on tactics, perhaps playing something that focus on it can be good for you ... Grünfeld rulez!

Hi Slates, TalJechin's "the most important thing is the motivation to actually do the work!" and your own "but I don't get as excited by it as I do the Grunfeld" just confirm that you've made the right choice. I'd second believing in one book whichever one it is. The Rowson book "Understanding the Grunfeld" is often mentioned as outstanding. Another point to stimulate confidence in the opening and therefore, in contradiction, give you more time to concentrate on the important parts of the game, is to cover "the rest". Again an often recommended book is Yelena Dembo's "Fighting the Anti King's Indians" which I believe covers everything after 1.d4 that isn't a proper KI or Grunfeld and even something against the English.


   

Thanks all so far. Each response encourages me as you all make valid points. Inn2, I feel that the Grunfeld definitely fits your criteria ii) and iii), but as yet I'm not sure about i).

I enjoy studying and playing the Grunfeld, but for years a lack of belief in my tactical abilities has led me to believe I must be more of a 'positional' player, so I have therefore shied away from tactical openings. For this reason I thought the NID/QID combo would be a better fit but I have never really enjoyed the position types as much.

I have tried the Nimzo on and off with various books from Emms' Easy Guide to his more recent Move by Move, but I don't get as excited by it as I do the Grunfeld. I suppose this is sufficient to say that I've answered my own question....but the input of posters here certainly helps, as I so often read that players below a certain strength shouldn't even attempt to play x opening, for example.

I guess I go with the Grunfeld and see where it takes me - as Laramonet says, I can judge it later, or have it judge me 

Katar, thanks for your encouraging words; I'll view your video when next at a computer, I just tried via the ipad I'm on now but of course IOS limits playback options on such devices, unfortunately, and it won't play.