I don't believe either choices differs. You will receive the same training points and elastic on other skills whether you train OD/ID each week or for the whole season. I'd prefer to train one for the whole season myself, just because training OD for a season will usually wield 2 maybe 3 ID pops from elastic effect depending on their ID. Also training OD then ID alternatively would mean your guy would be popping in both stats pretty slowly over the course of the season which doesn't sound like much fun to me.
But overall i wouldn't say either is worse than the other, its a choice of personal preference.