I'd add that front opening doors can be difficult because of what was mentioned (snakes flying out), however, that depends on the species. Additionally, they are easy and reliable. You can also open just enough to get a feeder in and use as a shield if you are worried about that. I use them on all my Boaphile tanks. I keep 2 corns, 3 boas, a Carpet Python, and a Ball Python. The boas are very aggressive feeders, but all my boa tanks have two doors. So I can open one the side the snakes head is not at. Having said that, I have room in my snake area to open the door with a hook and keep my distance. I also feed with long tongs and have had good luck so far with the boas honing in on their prey. Not too scared about getting bit when feeding based on knowing their routine and expecting the worst.
Front opening doors on Boaphiles are PVC and have some flex and don't break (easily). I've seen sliding doors that are glass and I do not love glass doors (weight and lack of give - if a snake misses or gets excited and strikes the door during feeding - see Feliz my BC). Do they offer PVC or Plastic doors that slide?
If you have the space and a hook and species that do not generally fly out of the tank, I like the front opening doors but prefer two for larger constrictors because it gives added safety.
Note/Edit: My doors open at the top and open down. Not a big fan of doors that open to the side and meet in the middle especially. Those are more problematic IMO.