We have a crib. We used it here and there when I decided i was done cosleeping and it was mostly a disaster. Mattress is SUPER firm and neither of my kids would sleep on it. I get that firm mattresses are safer, I get that, but I might as well have been putting them on a wooden board. Cripes. Also the slats were arm/leg traps and they'd constantly wake up with a foot stuck through the side and the bumpers were a nightmare because they'd still get tangled underneath them, or I'd find them with it over their faces- what's the point of a bumper, exactly? They're too small, IMO, and a baby can't even roll over in it comfortably without crashing into the side and waking up. If you have babies who don't move when they sleep or could easily sleep on the floor then they're probably fine but for my kids it's just a waste of money. For kids who need mama to fall asleep and are light sleepers that don't transfer well, a crib is a waste of money. Only way I could get my kids to sleep was to nurse them to sleep then sneak out without moving them so much as an inch, transferring to a crib just wasn't gonna happen.
Of course, you can't know any of this until after the fact. Some kids love sleeping independently and really do best in a crib, and for some parents crib sleeping is a requirement for everyone to live in a happy healthy household ... and for others you'll kick yourself for the waste-of-money crib. I'm currently using the sides of mine as a basement laundry rack and have no intention of setting it up for a baby this time around.
With cribs- there isn't much of anything to look at for safety. Most cribs are designed pretty similarly. There are very rigorous standards they have to pass. Look to make sure the rails are close enough together and won't come off. Make sure there isn't much gap between the sides and head/foot board. Make sure the bottom of the crib is easily adjustable (ie, don't have to take apart the whole dang thing to drop the mattress level!) Teething rails are pretty important for those chewy babies who don't shriek to be picked up the second they wake. Otherwise it's just asthetics- wood, carvings, stain, brand, etc.