Read through that thread or see this write up
As far as ata goes, ata 133 is no large improvment over ata100, and the same for 166. Similar to sataI and sataII, right now there nothing really getting sataII over the hump as far as technology goes to put it out in front of sataI.
Yup esata is external, but its performance is based only on theroy and possible peak rates. check it out.