What to look for/what type of Safety vest to buy?

Long Story short, three year old horses can be a great incentive to start seriously looking for a safety vest!
However, my expertise is in hunter/jumper land, and most people at the barn/tack store/in my general circle don’t own one, or haven’t owned one, and neither have I.
Since they’re relatively expensive and it’s important to get what one you buy right, I have decided to ask the experts. I need to find one for average sized woman, definitely heavily certified and preferably on the cheaper side (if possible, but also the thing to splurge on if it has to be splurged on).
Any help for what to stay away from/good experiences people have had would be great!
Also, is it a good idea to buy online or should I try to find a store that carries whatever brand I decide on (could take some doing in my area)?

I don’t qualify as an expert as I just bought my first one, an Airowear Outlyne, a few months ago, but I’ve been happy so far. I also live in an area where it was hard to try many on, and ended getting it online from Smartpak (good return policy). My criteria were similar to yours, but I’m pretty short so the fact that this came in a variety of sizes was appealing. It does fit very well and I imagine is about as comfortable as I could expect a vest to be. My only anticipated issue is that it will be hot…but I’m not sure if any are “cool” in the summer.