At the beginning of my career, I modelled my repertoire on Bobby Fischer’s. Not too original, I must admit, but I was so in love with his 6-0s, complete domination, and uncompromising attitude that I couldn’t help myself!
While studying his repertoire I noticed an important distinction between his White and Black repertoire. When he was White, he was more likely to vary his lines, for example against 1…e5 he could choose the King’s Gambit, 3.Bc4, and the Ruy Lopez, where he could further choose to play the main lines or the Exchange Variation.
Against the Caro-Kann he was notoriously undecided – from the main lines with 3.Nc3, to the Exchange with 3.exd5, to the King’s Indian Attack with 2.d3, and his old favourite Two Knights with 2.Nc3 and 3.Nf3.
In the Sicilian, apart from the trusted Sozin with Bc4 in various modifications, he also used the Rauzer (in the match with Spassky) and also the Keres Attack against the Scheveningen, the Fianchetto against the Taimanov, even the sharpest 6.Bg5 against the Najdorf (famously against Geller, a game he lost).
Things were different when he was Black, but only against 1.e4.
There it was the Najdorf and little else. There was a brief flirting with 1…e5 in the early 60s, but from then on, and until the match with Spassky, it was the Najdorf only.
Against 1.d4 he was keen to change more. From the King’s Indian and the Grunfeld to the Nimzo and QGD/Semi-Tarrasch. Even the sharp Benoni when required.
With this outline in mind, let us now take a look at how modern players are approaching their choice of openings.
Surprisingly (or not, if you like to view Fischer as decades ahead of his time!), their approach is almost identical to Fischer’s. The only difference is that apart from the Najdorf today there is also 1…e5 with the Berlin/Marshall combination.
However, some players, like Vachier-Lagrave until recently, had an almost Fischer-like (or perhaps Kasparov-like) repertoire, with the Najdorf against 1.e4, the Grunfeld against 1.d4 and with White 1.e4 (and then varying his approach in the sub-lines).
Kramnik (until his retirement), Aronian, and Carlsen (who settled into this approach after having his tries with other openings earlier in his career and who is more prone to change than the other two) are exclusive devotees to 1…e5 while against 1.d4 they do vary a bit, even though this variation is all within the most solid openings: the QGD/Semi- Tarrasch (re-introduced in modern practice by Kramnik at the London Candidates in 2013 and popular ever since), the Slav and the Nimzo.
With White, they are more flexible. Carlsen chooses both open and closed games while Aronian sticks to closed systems but changes his approach quite often (as lately, he has also ventured into 1.e4 territory). You could extend this analysis to other players like Anand, Nakamura, Caruana, and others, where you will see modifications, but the main strategy is almost always the same.
This short analysis paints a clear picture of how the majority of modern players construct their repertoires: with Black against 1.e4 they generally rely on one opening, which they have studied well and are not afraid to use against any preparation their opponents might throw at them.
Against 1.d4 they do vary a bit more but are always within the limits of the most solid openings.
With the state of modern theory being such that it is impossible to obtain an advantage with White, when they play White they are mainly going for the hit-and-run approach, choosing a line or idea suitable for one game, with the hope to surprise their opponents. Hence the need for frequent change in their openings and lines.
With Black, using the achievements of modern theory that shows no advantage for White, they are sticking to one solid opening as if taunting white to go forward and give them a chance from a counterattack.
Limiting your opening choices with Black has also the practical advantage of not scattering your attention because even within that one opening you choose there is so much to study. In this case, it is a matter of depth over breadth.
With White it is the other way round – breadth over depth – more openings are studied but with less depth since the aim is to use an idea or variation in only one game.