I was glad to see a thread of this nature, because it's the same question I've asked for months since I've "acquired" Chance, my adopted stray.
Maybe it's a slightly different situation, since Chance was a cat that hobbled into my garage and "chose" me, needing medical attention. Where he came from, I'm not sure. Now that he's healthy, it's quite apparent that Chance is the c.ock of the walk around here, and knows his way around the neighborhood. He has kitty friends and a wooded area across the street that he loves to frequent.
I've tried like mad to keep him inside. Understand, I would do anything to keep this cat safe. If something happens to him, I will have to endure the burden of guilt for choosing to give him what he wants in lieu of what will (likely) keep him free of external harm.
Chance is a big, strapping tom, with great reflexes, big ol' mitts, and a tremendous sense of adventure. I suppose he's like many cats in that respect, but when he's looked at me after he's grown bored of being inside, mrrrowing in that way, scratching at the door and giving me those big, green eyes, I have to give Chance what he wants. My heart breaks every single time I do it, but I trust him. I trust that he knows the risks, but knows that he needs his freedom even more.
Of course, Chance knows that come evening, it's time to come in for the night. If he's around anytime after 7 or so, he's brought inside the house. If we miss him, the doggy door to the garage remains open for him.
For as much of an obsessive fanatic as I am when it comes to my cats' health, I still like to think it's important to assess them as individuals. I like to think I've prepared Chance for the world as best I can. He's been fixed, gets all regular vaccinations, and has tagged indentification. I kept the flyers that I took down the last time he was gone for a few days. I'm prepared to keep putting them up when needed. Fingers crossed.
I feel like a heel even writing this, because I know how it must look to some; lazy and irresponsible. Mind you, I would never let my indoor cats outside under any circumstances, but Chance gives a vibe that I can't explain, I just can't keep him "caged" in good conscience. I love him too much. I've resigned myself to the fact that I could find him in the most horrific of conditions on any given day, but I am convinced that I have done the right thing by him, and that he loves me for giving him the quality of life he deserves.
I'm not sure this helped you in your desire to find answers, but I just wanted to share with you another (perhaps isolated, unfortunately) angle of your situation. No, I don't think you should let your cat out. But I do understand the weight of your dilemma and the many ways your love of your cat manifests itself in how you want them to feel about life.
I hope everything works out.