We use this when taking our dog to the vet or anywhere else.

Pros: holds well

Cons: can turn over easy

greatto use to transport smaller pets to the vet

Pros: great to use

Cons: none

I have 3 dogs who head for their crates as soon as I put my boots on, because if I am not home, that is where they feel comfortable, even if the crate doors are not closed.
The crates are from 3 different manufacturers, two wire, one plastic airline-style, all large enough for the dogs to sit in with their heads up unimpeded. Two of the dogs are over 100 lbs, their mother is about 85 lbs.
"Large enough" means that the dog can stand up, turn around completely, and should be able to lay down comfortably in the crate without being cramped. Our wire crates have slide-out trays; one is plastic, one is metal, and I definitely prefer the plastic one. It's lighter weight, has no sharp edges, and is less expensive to replace if it should ever crack. It's also quieter when the dogs step on it, and less thermo-conductive.
Our wire crates are also "drop-pin" style, meaning there are panels that all fit together at the coners and are secured together by one long wire pin at each corner. I tried the folding crate with the female pup when she was younger, and she was able to collapse the crate and get out of it. She worked the door latch on this one too (about 5 minutes after she first got in it, she was very proud of herself), so we made a long drop-pin latch with some rod stock, and now she watches carefully each time I take the rod out of the loops, but she can't reach the top or bottom of the rod from inside the crate.
The dogs had smaller crates, but had outgrown them by the time they were 8 months old. Before we had the larger crates, the dogs were housebroken, but would occupy themselves by shredding paper, or nosing into things that weren't theirs, or turning things into toys. Coming home to that would cause bad vibes between me and my dogs, and that wasn't fair to them. They had toys, but were easily distracted by things out the window, so window screens were torn, beds got jumped on, etc. They were acting like young dogs, unsupervised. As soon as I was able to, I bought the largest crates for them I could fit in our mud room.
Having the crates means I can come home and tell my dogs they were good dogs and how happy I am to see them every day, and we get to roll on the floor and do the pack greeting thing (after everybody goes outside ;-) ). The dogs quickly adapted to their new crates, with lots of praise for behaving themselves while I was gone. They often nap in their crates, take their toys to their crates, and don't like their crates moved when I clean around them. They feel secure in them.

Pros: Plastic trays safer and warmer, drop pin style more secure

Cons: Always get bigger than you think the dog needs.

Carrying small animals to the vet especially can be troublesome. They get nervous and don't like being in small cages and such.

Since I have gotten one of these little crates, my rabbit does extremely well in the car. He has some of his toys and blankets and feels at home. He can see me where in a box type carrier he cannot see very well.

I can also reach in and pet him with my fingertips.

These will work for cats and very small dogs.

Pros: Handy for small pets

Cons: Can be chewed

These are useful for many reasons. You can use these to take your pet to the vet. Our cat sleeps in one of these it is his "room". He loves it in there. He goes in there every night and has a smaller litter box in there, blankets, food, and water. His own little house.

Pros: Useful for vet visits.

Cons: Doors can rust.