If our choices have not (or had not) been predetermined, we are then free to be affected by random circumstances, i.e., by the randomness of probability as opposed to the determinedness (and thus pre-determinedness) of certainty. Freed from the fixed to the flexible; from reactive to proactive determining, perhaps.
So then, at least according to my logic, the choice at hand is not so much between determined or undetermined as it is between determined and predetermined. And the future limits of the predetermined lie somewhere between the certainties and uncertainties of oncoming time and the lines to be drawn there by its sequential changes.
As it would seem that, by well informed choices, we can willfully act to both determine and predetermine their effects for an uncertain period, but that the perfectly informed and active predetermination of anything, by anything, for all of time, should be seen as logically impossible.
The corollary to this is, of course, that what we choose to do today would seem to be for us, instead of for our past, to most willfully, successfully, and responsibly determine.