I've never gotten a true keratin treatment, but I do get regular Brazilian blowouts. They are different processes. The Brazilian blowout makes my hair very soft, silky, frizz free, and humidity resistant. My hair is flat for a few days after until the products wash out, and I do have to use texture pastes and sprays to get it what I want it to do, but its great for summer time because I can let it mostly air dry or just blow dry and go without spending time removing the frizz.
I pay about $200 for it, but they can be more expensive depending on the salon. The stylist first washes my hair with a clarifying shampoo, then lathers on the chemicals, then dries my hair slowly on cool air so the chemical sets. She then flat irons my hair in very small sections to set the chemical and make it frizz free. She then washes my hair again using a hair mask and blow dries it. Its a little bit of a process, and it sometimes can irritate my scalp for a day or two after, so just a caution if you have every sensitive skin. After, I use sulfate free shampoo/conditioner to help maintain it. The Brazilian Blowout brand makes a shampoo/conditioner I actually like the best, and that may be worth a try too even if you don't get the actual Brazilian blowout done.
With true keratin treatments, you cannot wash your hair or even get it wet for 72 hours after. Even with sweat. You also have to avoid kinking the hair or putting any bend it - no putting it behind your ears, in ponytails or clips, and you should use a silk hair cap or pillowcase while sleeping to avoid bedhead too. The Brazilian Blowout has no instructions after you leave the salon, other than to use sulfate free shampoo, so this is why I have never tried a keratin treatment. I can't speak to which one works better, but it would have to be a big difference for me to switch!