It completely depends who the two people are, first.
Then the design of the boat.
You probably can't get a more dyslexic, ADD stumblebum couple than us (nickname: Mr. and Mrs. Bumble). But we managed many thousands of happy miles , just the two of us, on our 56, into our mid-sixties. Handling-wise, lengthing it another 15-20 feet would not have made much difference at all, given the same design or better yet the same design with a cockpit. We looked at boats in the 70ish range but for us didn't see what it would benefit the two of us and occasional guests comfort wise, and we lived aboard full time for five and a half years, and it was a second home for another year. I could see it maybe if you were consistently going to have six to ten people staying on board. We used and cruised the thing all the time, year around In fact we saw nothing but extra expense, and more limitations as to where we could moor, dock and anchor. We were increasingly happier with our choice with every passing year.
As noted above the ergonomics of our boat made a huge difference; the walk around covered decks, the doors at each side of the lower helm, the near-perfect 360 degree visibility; even I could single hand the thing pretty effectively and wasn't afraid to do so. We had no desire to back into a slip; the boat really is not set up for it connections-wise and we prefer the privacy and views of having the aft deck and the master cabin on the fairway. I did have to back in a few times but with Ann stationed back there it was no big deal. Having a set of real stairs to the flying bridge was an excellent add on by one of the POs.
There is a great saying, I believe coined by the cruising guide author Skipper Bob "Don't buy the biggest boat you can afford, buy the smallest boat you can be comfortable in" That means different things for different people. For us that was the 56. Others I know, a 36. Maybe you, a 70.