Both lines, an Calgary-Edmonton line and HSR and upgraded service in the corridor, make sense. The Alberta HSR would be from a techincal standpoint easy to do so it would not be an expensive project (in relative terms) so the fact that its length serves a smaller population is somewhat offset. The corridor is going to be more expensive to construct in (though not excessively more), but the benefits from an HSR line and local upgrades would be enourmous. It is hard to compare the two projects side by side but while the Quebec-Windsor corridor would certainly bring about far greater changes and benefits in passenger transport, the Alberta project still has merit.
If the federal government were to help fund an Alberta project, then you are right, there is no reason they should not also fund a corridor project (and they probably would as part of an overall rail investment funding package). But that means Ontario and Quebec politicians and leaders are going to have to take some iniative and start pushing for such a project. Otherwise the whole thing will be left to the passing fancies of the Federal government and if that is the case it will be a long time before HSR ever gets off the ground.