Of these 3 I have played DL11, but never integrated it with the campaign (our Dragonlance campaign back in the 80s was already through book 2 before the product was released). With Conquest I finally have a chance to integrate a wargame with an RPG campaign. The basic idea is that we (the RPG group) would play the game and have the results of the game impact the RPG campaign and have the stuff the party does in the RPG campaign affect the wargame.
There are basically three ways I can see to do this.
1) Play the game and have the situation at the end of the game be the starting point for the campaign.
2) Have the war going on at the same time as the campaign. For example, one turn in the wargame could be a month of RPG time.
3) Having the RPG campaign create the initial setup of the wargame.
Conquest should be the best produced and polished of this type of product since its primary purpose will be to be a wargame. The others (DL11, X10, and and GW) were RPG supplements first and wargames second.
Also, Conquest will have an actual boardgame board (the others had paper boards) and plastic miniature to represent the armies (the others all had small cardboard chits). This is definitely THE D&D product I am most looking forward to this year, and I hope it doesn't disappoint.