I think it also needs to be said that location plays an important role in the debate between sliding versus swinging. In the intance of my ex's bearded cage, she could have opted for swinging doors, because space wasnt a huge issue, but she felt that aesthetically and safety deemed sliding was better.
Photographing the little jerk can be a pain in the butt with the sliding doors, because he always seemed to like to be infront of the one that was closed

But aside from that, we both felt that it provided enough access to the enclosure without leaving the entire enclosure vunerable.
That said, my brother and I are going to be redoing his bearded's cage, which currently only has top access.
I can offically say that while having top access is nice,
only having top access is a pain in the rear, especially once the enclosure was elevated off of the ground. In his bearded's new enclosure, we purchased a curved piece of glass with frame for the front (similar to a display case at a grovery store) and the entire thing is going to open upwards with the aid of gas-struts (similar to the deck lid on a car). This will provide nearly 100% access to the cage without a frame at the top to make it difficult to maneuver around in.
I'll have to scan the "blue prints" we have drawn up to illustrate what I'm referring to.
But in the case of my iguana's enclosure (I know, not a beardy but bear with me) swinging doors simply weren't an option. Due to the size of the doors, and ammount of access I needed/wanted to the encosure, and various other obstructions, sliding doors were the
only choice.