I'd go with a reclining sofa. A sofa would look aesthetically better than just a regular bed. Also, if you end up using your home theater with guests, it would be easier to fit multiple people on a sofa than having everyone cram onto a bed.
I'd be choosing the reclining sofa because I think that it would be more convenient eating the movie snacks while on it. It would also be harder to fall asleep there since the space wouldn't be so big.
I've tried watching movies while in bed and only ended up using pillows to have that reclined position. It was inconvenient since the support on the head wasn't as stable with only the pillows. So for sure that when watching movies, a wide reclining sofa would work for me.
A reclining sofa similar to some gaming chairs would be convenient because you can even control the angle of your vision while avoiding any strain on your neck. It lets you relax that the next thing you know, you're probably asleep.