Well defining the best proxy is strictly connected on what you intend to use it for however if you are looking to protect your privacy and/or using SEO tools like SENuke or other automated submitter program you need highly anonymous dedicated IP proxies.

In other words you need proxies with IP's exclusively assigned to you and that are highly anonymous so that the proxies you use do not identify themselves as proxies to websites and third party software. Your connection trough them will look just as you were connecting to the web at the location of the proxy.