Yitzchak's Bracha for Eisav
With this background, we can now return to our question: What is the nature of the blessing which Yitzchak intends to give Esav? Is it a blessing of bracha or bechira?
Considering that there appears to be no reason for Yitzchak to choose only one son, we should expect that the nature of his intended blessing of Esav to be a bracha (and not bechira).
To determine if this assumption is indeed correct, we need only examine the actual blessing which Yitzchak gives, i.e. the blessing to Esav which Yaakov took by trickery:
Why then does Yitzchak (intend to) bestow this blessing only on Esav? Why can't both sons be blessed?