I prefer backpacks, but I have also used travel cages too. I have had two different backpack carriers for my birds, I really like both of them, but I prefer (and honestly the birds do too) this one which I got recently:
It's sturdy and I like that it has a clear front, but also has the darker piece of material that you can put over the front if needed. And it has decent ventilation on the sides, it also has a stainless steel food cup, but not a water cup. But there is a water bottle holder and hole for the water bottle to go through on the side of the carrier. I really don't like using water bottles, but I found a glass one on Amazon and it is only ever used for short times and works well with the carrier. I'm trying to figure out a way to change the perch to a natural wood branch or something too eventually, instead of the dowel. I've also added toys to it and my cockatiel has really liked it so far.