I haven't heard much about Landmark, but from what I can find on the Internet they seem to be your average company. On the Energy Star Canada web page they have just a few windows listed. The windows that they have listed do show good numbers, but anyone showing windows with only hard coat low e, no grilles and mainly triple glazed windows will also get these or better numbers. Their web page talks about a lot of thing, but these are mainly generic things that any average window company will do eg: triple seals, welded sash, multi point locking etc. They also say that they have an exclusive integrated crank, this is the Truth Maxim that anyone can use.
As to Ducana, I do know a fair amount about them. They use the Rehau extrusions. The vinyl is as good as it gets, the problem with it is in the design of the profiles, and the way Ducana builds it. Most if the things that are used as selling features, foam filling of the chambers etc, are done to be unique so there is a selling feature. Unfortunately there are a few problems with this. First of all foam filling of the chambers is not recommended by the extruder of the vinyl, also foam filling of a multi chamber window will actually slightly decrease the insulation value of the frame and sash, not increase it. They push triple glazing, warranty, $ 100 referral's, energy star etc. With all of this why do they only list 8 windows on Energy Star and they all use hard coat low e, triple glass, and krypton filled units. This will give some good numbers to advertise but doesn't reflect what most people buy. For numbers see North Star windows, with hard coat low e, triple glazed, and krypton filled these numbers are higher than Duncana's. What about the people who want grilles, don't need or want triple glass or krypton fill due to it's very long return on investment. Ducana doesn't seem to cater to these customers.
Being in the Kitchener area maybe try a Strassburger dealer, or if you like the Rehau vinyl find a Euro Vinyl dealer, they build it better than any other of Rehau's dealers. If you are looking for higher Energy Star numbers try a North Star dealer.
From what I know about Ducana, and what I can see with Landmark you have found 2 companies that offer a lot of sizzle, but very little steak.