It depends on what you mean by best. For the average user a phone with a snapdragon 400 with 2 gigs of ram should be enough. If however you are a power user a snapdragon 800 series should be enough with 2 gigs of ram. The fastest CPU so far is the snapdragon 805 which is used in the GS5 LTE-A. I should also note that anything more than 2 gigs of ram is only needed if you take a lot of high resolution photos and videos
You really have to figure out which phone you want for your provider, and read the reviews. There's more things on a phone to worry about then CPU and RAM, like screen and battery life.
Sounds like you want a high performance phone so just get an HTC One M8 which is sleek and stylish and has outstanding performance. (coming from someone who owns it) Also battery life is fine and the IPS panel on this thing is sharp and vibrant. Great phone but boy did it cost a load.
It depends on what you mean by best. For the average user a phone with a snapdragon 400 with 2 gigs of ram should be enough. If however you are a power user a snapdragon 800 series should be enough with 2 gigs of ram. The fastest CPU so far is the snapdragon 805 which is used in the GS5 LTE-A. I should also note that anything more than 2 gigs of ram is only needed if you take a lot of high resolution photos and videos