If I have to rank by which is the more effective then.
1. Slav. This is the strongest out of the 3.
2. QGD
3. QGA
But I think that QGA is the easiest to play.
QGD, QGA or Slav?
Sort:
This list is personal preference, not what I believe to be theoetically best.
1.QGA
2.QGD
3.Slav
The idea of the QGA shouldn't be a pawn win. Ill explain the advantage of dxc4 in a simple way. In the QGD or slav, the main breaks black aims for are e5 or c5. In the slav c6 is already played, so you spend a tempo on c5. In the QGD e6 is already played, so similarly e5 costs extra time.
With the QGA black sacrifices his hold on the centre, but in return hopes to play e5 or c5 in one move, effectively saving time.
I think the QGA holds equal merit to the QGD and slav as an opening below GM level, however it has less lines to learn, is probably easier because of this, and often white players arn't very well prepared for it.
Also it is the most likely of the three to get into an early endgame, and I very much enjoy endgames.
Rank the three mentioned as to which is your preffered opening and why?
1.Slav (Gives the most Closed Positions to me, an interesting end game)
2.QGD ( Can transpose into a KID, but Slav is better to me)
3.QGA (Losing position and a queen's pawn for a temporary pawn win)