I’ve ruined 3 helmets the hard way. In 1993 a car pulled out from a stop sign in front of me. I hit the front tire; flew over the hood; and did a 3-point landing: two hands and my head. I got up and walked away - mad but alive. About the only thing that didn’t hurt was my head. The helmet exploded into many pieces absorbing the impact. It was later used in a bicycling safety training course for grade school kids. The EMTs who treated me had also treated a motorcycle rider who had a similar accident the day before. The main differences was that he didn’t have a helmet on and he was still unconscious when they got him to the ER.
In my very last bicycle race, I crashed bad and suffered a broken rib, punctured lung, and a minor concussion. It was minor due to the helmet.
As far as what helmet to buy, all helmets sold in the USA must meet the minimum safety requirements which are pretty strict. There’s some discussion that cheaper helmets may actually provide more protection than the super-light, many vents, expensive models.
The more vents the better if you live in hot places. BTW: I’ve done the Hotter 'n Hell 100 in Wichita Falls, Texas. If you have a road bike where you are bent over pretty far, I wouldn’t recommend a visor. If you are sitting upright, visor is OK. Some helmets have removable visors. You will probably still want sunglasses on bright days even with a visor.
A lighter color helmet might be cooler in direct sunlight. You don’t want a black helmet anyway as a brightly colored helmet can make your more visible to cars and other riders.
BTW: The “replace a helmet every 3 years” rule is pretty much BS. Back in the day the foam used in helmet did deteriorate pretty quickly, but not the newer stuff. If you store your helmet in a car, keep it out of direct sunlight and heat as much as possible.
One thing is for certain, if you do bang your helmet hard in a crash, replace it especially if you can see any damage such as cracks. They are made to absorb an impact once. A new helmet is cheap insurance.