The advantage is also that white is in big risk of facing  mating attacks too. In both 6. Bg5 and 6. Be3 White is risking the entire life basically by trying to rush with kingside attacks by risking the own king. Najdorf always works two ways

Okay, I play both regularly so maybe I have some ideas

Najdorf:

The Najdorf is extremely theoretical, and you need to bust your memory to survive. When I was 13 years old, I remember trying to memorise the 6. Bg5 Poisoned Pawn chapters of Nunn's old 1996 book. Thinking that it would never happen I just did it anyway for completeness. One day someone played one of the main lines and I needed it past move 25. 

Then in 2003 a shocker was announced in the main line Poisoned Pawn with 15...Be7 with 17. Rf1!! and there was a mass of analyses in New In Chess (I think that it was this one, the YB), where it went past move 35 and even 40. I tried to analyse all of it but I lost twice against two titlted players because I just messed up my memory completely. My brain hard drive failed and lost in literally 45 minutes. My opponent told me, "YOu should have memorised the last New In Chess YB lines!"

Go to February 2015 and Negi has a almost 400 page book on 6. Bg5 for White. You have to memorise a lot of stuff as Black, but now there is the interesting 6...Sbd7. Still, you must be willing to bust yourself to memorise and memorise to play the Najdorf. There is also 6. Be3 and the extremely popular 6. h3, which seems to now have more theory than 6. Be2 at this rate.

My 6...Sbd7 ChessBase file is dated from November 2014 and is still on analyses. I often run the computer overnight with Stockfisk for critical lines.  Sack is, are you willing to do this

Kan:

I play the Kan with 5. Bd3 Bc5 6. Nb3 Be7, like Hellsten. I like it very much, and it is nowhere near theory of Najdorf. If you like to just play a setup Sicilian with (relatively!) lower thoery than the others and then counterattack in the moves between 15-25, then the Kan. Of course there is theory, but natural moves in my experience seems to be commoner in Kan than Najdorf because you do not really put Houdini and Stockfisk to move 40 in many Kan lines. 

About 5. c4: this really does not scare me. I play the Hedgehog, but there is a very big difference. I hate the Maróczy Bind with the bishop on g7 (Accelerated Dragon setup) because ...d5 is alomst impossible. Hedgehod has pawns on d6 and e6 and you play for ...d5. White often gets overextended here, so if you are good in close quarters, just play the Hedgehog against 5. c4.

For those that are interested in Jesus de la Villa's book "Dismantling The Sicilian: A Complete Repertoire for White" (2009) he only gave three Sicilian variation a full 5* rating on a scale from 1* to 5*'s.

They were the: Kan, Najdorf and Sveshnikov.

This is a small sample of the introduction he gave for them:

Sveshnikov

The Pelikan Variation has become one
of the most popular of Sicilian variations.
In spite of its anti-positional appearance,
it is very appealing to players
of all levels, due to the activity achieved
by the black pieces. Perhaps its only
drawback, from a practical point of
view, is that a white player with some
theoretical knowledge has several options
to play for a draw. Up to this moment,
all refutation attempts have been
to no avail, and the trendy variations
have been shifting.

Kan

The Paulsen Variation is one of the
great systems within the Sicilian Defence.
It has a long and successful history,
having resisted not only all refutation
attempts but even all attempts to
guarantee a comfortable, even if slight,
plus for White. The typical positions
are strategically complex and ideal for
playing for a win against all kinds of
opponents.

Najdorf

The Najdorf Variation is acknowledged
as the most important Sicilian system,
and its great merit has kept this appreciation
for some decades. Can we state the
reasons for this? For sure, its theoretical
viability is one, but also its apparently inexhaustible
potential to lead to positions
rich in tactical and strategic themes,
which guarantee hard-fought games and
chances to play for a win as Black.

OK, say I play the Kalashnikov with 5.Nb5 d6 6.N1c3 a6 7.Na3 b5 8.Nd5 Nge7 9.c4 Nd4 etc. and the early ...f5 lines against 6.c4 (this actually was my Black repertoire for a while many years ago, though without much success!). Surely you agree that Black must play for the initiative in these lines, or else his weaknesses will just kill him?

The same is very much true of the Löwenthal line with 5.Nb5 a6 6.Nd6+ Bxd6 7.Qxd6 Qf6 (even if White exchanges queens) and many of the sharper Sveshnikov lines.

To my mind the Sicilians that most often rely on the initiative for Black are the ones based on an early ...e5: The Sveshnikov, Kalashnikov, and Löwenthal. With that hole on d5 and backward pawn on d6 (and often other positional weaknesses or sacrifices) Black just has to play actively to stay alive!

Though there are calmer lines even in these openings; many of TonyRo's line choices in his recent Kalashnikov book "The Killer Sicilian" are on the solid side for that variation.

The Dragon also requires Black to play actively, but it's hard to say who has "the initative" in some of the wild main lines with opposite-side castling. Maybe "both"!?

fling wrote on 04/20/15 at 08:31:46:

I know you're right but I play chess for fun I don't want to suffer defending 50 moves to eventually draw, at best, with black. So, isn't it possible to play dynamic chess with the black pieces?

Sorry you're right, I meant the Taimanov, I've corrected the post. I don't mind to study theory but I like to have the initiative at any cost.

I've been a Najdorf devotee for many years but it seems I haven't been able to find a good antidote against the 6.Bg5 variation. I hate the Poisoned Pawn. I've played both Kasparov's 7...Qc7 and the flexible 6...Kbd7, with poor results. So lately I'm thinking to pick up the Kan, mainly because I think I will not face such fierce attacks, and I can also combine it with the Taimanov. Do you think the Kan could give me the same winning options as the Najdorf with less risk of being crushed by mating attacks?