Formula question


Is it okay to switch formula? My son was on enfamil nuro pro for like a week and I switched to enfamil gentlease because he would projectile vomit and I’ve notice he doesn’t really like enfamil gentlease. He not happy with the taste of it sometimes he even gags and won’t drink more than 2 Oz. He is 6 weeks old. I have similac samples. Is it okay to try them today and see if he likes it ?

Edit: which one is better?