They do not match each other, but they do have an autopen look and feel. I suspect they are two different autopen patterns.
Autopen IMO. This is one of the standard stock pics he sent out around this time, and while it's not out of the realm of possibility that these are both legit, I've stayed away from similar pics precisely because I can't ascertain legitimacy.
This pic looks to have been made during his second term -- here's a piece I have from the similar time period (mid-late 70s) with his auto..
A similar piece from the early 70s that may also be of help -- though I can't confirm full legitimacy of this piece. I bought it as part of a larger collection owned by an individual who appeared to know the Trudeau family (the same seller I bought it from sent me a handwritten condolence card from fellow PM Lester Pearson's wife, and one from the Trudeau family after P.E.T.'s death), it was being sold at a very decent price, and it had the mailing envelope in fantastic condition to boot.
From what I understand, this was one of the few time periods where P.E.T. had uninterrupted time to respond to well-wishes -- he took off a month or so after his son Justin's birth, and there were (to my knowledge) at least two separate batches of letters he responded to.