For Phantom sites, you are generally better off choosing proxies located in the US, unless the site region locks, in which case you should purchase proxies located in the region that site is hosted in/region locks in.
Optimally, you want to purchase proxies that are located closest to you or your server. For example, if I live in New York or have a server located in New York, East Coast proxies are the best for me (NY, CHI, VA, etc.).