O.k., this is just my experience and opinion. If you have cat that will wear the collar, it is worth having them wear one, especially if they express interest in escaping.
In '97 we moved to the East Coast and took our cat with us. We lived in a 2nd floor apartment that had a similar door situation as you described. She had been an indoor/outdoor cat over the course of her life, but had been an indoor cat for us, as we have always lived in the city. In this apartment building, cat had to get out our door, through the end hall door (usually open), down the stairwell and out the front door that was always locked. Well, she succeeded twice in getting outside. The first time, she came back after a few days. Likely, she didn't go far and it just took me a couple of days to spot her and catch her. I should have collared her then, but didn't. The 2nd time however, she wandered about five miles away into the next community over. She nipped a girl who was feeding her and was picked up by the pound. We searched everywhere for her, and reported it to the local pound. They never called us. However, she was picked up (as I mentioned). DH caught a lucky break and found her in the "bite" room about a week after she disappeared and a few days before she would have been euthenized. It ended well, but it was heartbreaking to think that we had lost her and could have prevented much of the trouble by collaring her.
My current cat (a different one) will not wear a collar. He makes a break for it frequently, but has only succeeded in getting outsde unnoticed once. I found him sitting his fat 14# butt on my front poarch when I got home. If I could keep a collar on him, I would.
Mama to three small people; wife to one big person; pet-person to cats and dogs..."Be the change you want to see in the world"-- Gandhi