Slav or Semi-Slav

Hi. I am looking for a solid defense to 1. d4. I like the looks of the Slav/semi-slav systems, but am looking for an opinion as to one vs. the other.

i like the dutch defence. 1. d4  f5

you have a lot of possibility... the Slav et Semi-Slav, the Nimzo-Indian defenses, the West-Indian defenses, the East-Indian defenses de Grünfeld defense and the Modern Benoni...

A lot of thing you can look and learn

I guess what I am asking is what are the main differences between the slav and the semi?

Sorry...I'll see what I can find on those openings

The Semi-Slav is both more popular, and in some of its line (eg. Botvinnik, Noteboom, Marshall gambit) sharper.  Anand, Kramnik, Ivanchuk and Shirov all play the Semi-Slav.  The Slav is probably a solid choice, but it hasn't been getting as much attention lately.  Smyslov used to play the Slav, and Morozevich dabbles in it now.

What do you mean? The Slav was just used by Anand in a few 2010 WC matches. Or do you mean that it hasn't been getting attention as in not many new novelties, new lines, etc?

Other than that, yea...Semi-Slav is a lot sharper than the Slav. Look at the Botvinnik or Moscow Variations for example.

Queen's Gambit declined Orthodox variation, is quite deep and logical if you delve into it's mysteries.

The Slav is probably the most flexible d4. opening. It can be impregnably solid, like the line seen in the Anand-Topalov match, or it can be like, for instance, the Semi-Slav, which is notorious for its theoretical dependence and its utter complexity, particularly the Botvinnik and the Anti-Moscow Gambit (and the Meran, sometimes).

Although, if I'm not mistaken, the solidity of it isn't guaranteed without deep positional awareness and White's acquiescence.

I guess Anand and Kramnik do play the Slav a fair bit.  It was just an impression that the Semi-slav is an extremely popular main line defence while the Slav seems a little more like an offbeat surprise weapon.

The slav is more solid then the semi-slav but it's still very counter attacking and by no means a drawing weapon. You can fight for a win in every line, even the exchange variation. A very good book on it is Play the Slav by James V. I find the slav lines much more intuative and easy to play then semi-slav. You get your "bad" bishop out to an active square and you get counter play along with fairly clear cut plans in the middle game.

I may look into that. I play the French against 1. e4, so I like to play 1. d4 e6 so as to give them the chance to transpose into the French with 2. e4.

If you don't mind the transposition back into the French from 1.d4 e6...if, in fact, you openly court it...AND you're looking for solid defenses, then you have excellent and compatible choices for the d-pawn openings.

3.Nc3 Nimzo

3.Nf3 QGD or QID

Alternatively, you can use 1...e6, 2...f5 and transpose into a Stonewall Dutch.  Which has the multiple benefits of being aggressive against a poorly prepared opponent, solid against a better opponent, comparatively little theory, the flexibility to play it against stuff like 1.c4, and probably the best book on an opening for black to come out in ages, in Win with the Stonewall Dutch.

The semi-slav is probably a bit sharper...really saying anything more than that would be a useless generalization. I suggest trying out both openings to see which you like better, both are first class defences to 1.d4.