As, I guess, most people upload and leech from FiSe, HF and FiSo, Softlayer (I am currently on a Dallas RDP) is probably a very good choice.
But there is no 'best' server in this scenerio. Someone who uses Rapidshare or other EU host, might be better served with a EU RDP.
But there is no 'best' server in this scenerio. Someone who uses Rapidshare or other EU host, might be better served with a EU RDP.