Sliding is easier to control remotely while still having it be automatically fairly predatorproof when closed (you can weight it, let it drop down by a simple pulley system to open/close, and when it's closed the bottom edge can drop behind a strong board so that raccoons etc can't pry it out or slide it up). (A positive locking system is even safer, though).
Hinged can provide a useful little 'porch roof' over the pophole if you install it that way, to reduce rain getting in. To latch it at night you really need either a bar that slides over the opening, or a strong raccoon-proof (or inside) latch.
No matter which way you go, make sure to think about where shavings will fall when the door is opened in the morning and whether they will be jamming where the door wants to *close* in the evening. You want the opening designed so that spilling-out shavings fall cleanly away, rather than collecting where the edge of the door will later be supposed to close against.
Hope this helps,
Pat